UC-NRLF 


SB    2h    31fl 


THE  CAR  WHEEL 


This  book  is|  the  property  or 


and  is  sent  with  1  tke 


IFT  OF 


- 


THE 

CAR    WHEEL 


GIVING  THE   RESULTS   OF  A 
SERIES   OF    INVESTIGATIONS 


BY 

GEO.    L.    FOWLER,  M.  E. 


«a& 

IUCHAfiDB.GAB& 
Mante£«r  of  Sale*, 
Crocker  Building, 

San  Francisco  -  Cat 


PUBLISHED  BY  THE  SCHOEN 
STEEL  WHEEL  COMPANY 
PITTSBURGH,  PA.,  1907 


Copyright,  1907,  by 
THE  SCHOEN  STEEL  WHEEL  COMPANY 


/,x 

H^  ' 


The  Fleming  Press,  New  York 
10726 


• •       *••••          e        % 

£JG*!1V:/*W: 


435963 


4  •  •««.«. 


FOREWORD 

The  solid  forged  and  rolled  steel  wheel,  referred 
to  in  the  following  pages  of  this  book,  was  devel- 
oped and  first  manufactured  by  Mr.  Charles  T. 
Schoen,  the  pioneer  builder  of  high  capacity  steel 
freight  cars,  and  former  president  of  the  Pressed 
Steel  Car  Co. 

In  the  exploitation  of  large  capacity  cars  Mr. 
Schoen  was  confronted  with  the  problem  of  getting 
wheels  to  meet  the  requirements.  The  cast  iron 
wheels  put  under  these  ioo,ooo-lbs.  capacity  cars 
failed  repeatedly  and  the  situation  became  serious. 
For  instance,  one  railroad,  which  had  in  service 
several  thousand  of  these  cars,  at  one  time  con- 
sidered the  expedient  of  marking  all  of  them  down 
to  8o,ooo-lbs.  capacity  in  order  to  reduce  the  load 
on  the  wheels. 

The  majority  of  wheel  failures  occur  on  moun- 
tain roads  with  steep  grades  and  sharp  curves  where 
long  and  heavy  brake  applications  are  necessary,  and 
the  wheel  flanges  are  subjected  to  severe  shocks. 

Steel-tired  wheels  had  given  satisfactory  service 
under  passenger  cars  running  over  these  mountain 
roads;  but  they  were  out  of  the  question  for  freight 
equipment  because  of  their  prohibitive  cost.  The 
economical  value  of  the  high  capacity  car  to  the 
railroads  having  been  demonstrated,  the  problem 
was  to  produce  a  wheel  equal  to  or  better  than  the 
steel-tired  wheel  in  strength  and  at  a  cost  for  mileage 
less  than  that  of  the  cast  iron  wheel. 

Mr.  Schoen  began  his  experiments  in  1898,  and 
early  in  1901  the  first  machinery  for  making  these 


wheels  was  designed.  The  Schoen  Steel  Wheel  Co. 
was  organized  on  May  n,  1903,  and  the  business 
of  making  solid  forged  and  rolled  steel  wheels 
established  for  the  first  time  on  a  commercial  basis. 

The  enterprise  has  been  a  success  from  the 
start,  fully  justifying  the  large  expenditure  of  money 
required  in  development  work,  and  for  the  installa- 
tion of  the  necessary  machinery.  At  the  present 
time  the  company  has  a  plant  in  operation,  located 
at  Pittsburgh,  Pa.,  capable  of  producing  250,000 
wheels  a  year,  and  in  connection  with  it  open  hearth 
furnaces  with  an  annual  capacity  of  100,000  tons  of 
steel  for  making  the  blooms  from  which  the  wheels 
are  forged  and  rolled.  The  entire  process  from  raw 
material  to  finished  wheels  is  under  the  direct  con- 
trol and  supervision  of  the  company. 

The  Schoen  solid  forged  and  rolled  steel  wheel 
has  proven  such  a  pronounced  success  in  America 
that  it  has  attracted  the  favorable  consideration  of 
foreign  railways.  To  supply  this  European  and 
Colonial  demand,  The  Schoen  Steel  Wheel  Co., 
Limited,  of  Great  Britain,  was  organized.  The 
works  are  situated  in  Leeds,  Yorkshire,  and  have 
an  annual  capacity  of  100,000  wheels. 


Schoen  Steel  Wheel  Co. 


Pittsburgh,  Pa. 
November,  1907 


PREFACE 

When  this  investigation  of  wheels  and  tires  was 
first  undertaken  its  ultimate  scope  had  not  been 
decided  upon,  and  it  was  the  expectation  that  it 
would  end  when  the  first  few  comparative  results  had 
been  obtained.  It  was  made  solely  for  the  purpose 
of  securing  information  regarding  the  standards  of 
quality  of  metal  and  workmanship  that  must  be  met 
in  the  development  of  a  new  industry,  the  success 
of  which  depended  on  the  production  of  a  wheel 
that  would  at  least  meet  the  present  requirements  of 
railroad  traffic.  There  was  no  intention  of  publish- 
ing the  results,  and  this  accounts  for  the  apparently 
unfinished  condition  of  much  of  the  work.  As 
soon  as  sufficient  data  had  been  obtained  in  one 
line  of  investigation  to  serve  as  a  working  basis, 
attention  was  turned  to  another  branch  of  the  sub- 
ject. Results  obtained  in  the  various  tests  referred 
to,  therefore,  must  not  be  accepted  as  complete,  but 
the  records  of  the  work  so  far  done  are  made  public 
with  the  thought  that  if  they  serve  no  other  pur- 
pose the  attention  of  railroad  officers  will  be  attracted 
to  the  field  of  railroad  dynamics,  as  yet  unexplored. 

In  the  presentation  of  the  results  obtained  no 
attempt  has  been  made  to  harmonize  them  with  pre- 
vious theoretical  deductions,  nor  has  any  attempt 
been  made  to  build  a  theory  upon  them  as  a  basis. 
Only  elementary  mathematical  calculations  have  been 
introduced  in  order  to  show  about  what  can  probably 
be  expected  from  a  continuance  of  investigations 
along  the  same  lines. 

Such   a   piece   of  work   as    this    could    not,   of 


necessity,  be  carried  on  without  material  assistance 
from  the  railroads,  wherever  track  and  rolling  stock 
was  required,  or  defective  and  worn-out  material  was 
to  be  obtained.  Such  assistance  has  been  generously 
and  cheerfully  given  whenever  it  has  been  asked  for. 
Acknowledgments  are  due  to  Messrs.  A.  W.  Gibbs, 
D.  F.  Crawford,  Wm.  Mclntosh,  G.  W.  Wildin, 
J.  F.  Deems,  and  Prof.  Wm.  Campbell,  for  materials 
furnished  for  examination  and  for  assistance,  and  to 
Messrs.  E.  G.  Ericson  of  the  Pennsylvania  Lines 
West,  J.  E.  Childs,  E.  Canfield  and  G.  W.  West 
of  the  New  York,  Ontario  &  Western,  and  J.  F. 
Deems  of  the  New  York  Central,  for  the  use  of 
track  and  rolling  stock. 


GEO.  L.  FOWLER, 


New  York 
November,  1907 


D 


ESIGN  OF  THE  SOLID  FORGED 
AND  ROLLED  STEEL  CAR 
WHEEL. 


WITH  a  wheel  made  of  one  solid  piece 
of  steel  having  the  requisite  physical  properties,  it 
follows  that  a  design  can  be  used  differing  radically 
from  a  wheel  having  the  center  and  the  tire  separate. 
The  tire  of  a  steel-tired  wheel  must  be  of  such  a  thick- 
ness that  it  will  admit  of  a  reasonable  amount  of  wear 
and  at  the  same  time  leave  enough  metal  in  that 
part  of  the  tire  which  is  scrapped  to  insure  strength 
against  breakage  during  the  last  days  of  the  life  of 
the  wheel.  With  the  solid  forged  and  rolled  steel 
wheel,  having  the  rim  integral  with  and  stiffened 
by  the  web,  more  wear  can  be  safely  allowed  than 
where  the  stretching  or  breakage  of  the  tire  under 
the  rolling  and  pounding  action  of  service  must  be 
provided  against.  The  solid  forged  and  rolled  steel 
wheel  resembles  somewhat  the  cast  iron  wheel  in 
section,  the  difference  being  in  the  web,  where  there 
is  a  single  plate  instead  of  double  plates  and  no 
brackets  as  in  the  standard  cast  iron  wheel. 

The  details  of  the  dimensions  of  car  wheels  vary 
with  the  requirements  of  the  railroads  using  them. 
There  is  a  wide  difference  of  opinion  as  to  the  best 
proportions  for  the  thickness  of  the  rim,  while  the 
dish  and  length  of  hub  are  determined  to  a  great 
extent  by  the  details  of  truck  construction.  This  is 
especially  so  in  electric  railway  work,  where  the  wheel 
must  be  made  to  fit  in  between  the  motor  on  the 
inside  and  the  journal  boxes  on  the  outside.  Ordi- 
narily the  dish  of  the  wheel  is  determined  by  the 


SOLID    FORGED    AND    ROLLED    STEEL  WHEEL    FOR    ENGINE    TRUCK. 


SOLID    FORGED    AND    ROLLED    STEEL    WHEEL    FOR    ENGINE    TRUCK. 


-36' Of*. 


SOLID    FORGED    AND    ROLLED    STEEL    WHEEL    FOR    PENNSYLVANIA    R.R. 


JL 


SOLID      FORGED    AND    ROLLED    STEEL    WHEEL    FOR.  AMERICAN    CAR    AND 
FOUNDRY    CO. 


SOLID    FORGED    AND    ROLLED    STEEL    WHEEL    FOR    TRAILER    TRUCK 
INTERBOROUGH    RAPID    TRANSIT    CO. 


SOLID    FORGED    AND    ROLLED    STEEL   WHEEL    FOR    ELECTRIC   STREET    CARS. 


SOLID    FORGED    AND    ROLLED   STEEL   WHEEL   FOR    ELECTRIC   STREET    CARS. 


/O' 


SOLID    FORGED    AND    ROLLED    STEEL   WHEEL   FOR    CLEVELAND    AND   SOUTH- 
WESTERN   TRACTION    CO. 


SOLID     FORGED    AND     ROLLED     STEEL    WHEEL    FOR    PHILADELPHIA    RAPID 

TRANSIT    R.R. 


size  of  the  journal  box  and  its  location  relatively  to 
the  tread;  but  the  form  given  to  the  web  dishing, 
the  thickness  of  the  rim  and  the  size  of  and  shape  of 
the  flange  and  tread  are  matters  for  individual  con- 
sideration in  each  case. 

In  wheels  intended  for  steam  railroad  service  the 
treads  and  flanges  are  uniform,  corresponding  to 
the  M.  C.  B.  standard.  The  variations  in  design 
are  found  in  the  webs  and  hubs,  the  thickness  of 
rims,  and  occasionally  a  variation  in  the  height  of  the 
flanges  is  allowed  if  the  wheels  are  intended  for 
engine  trucks. 

Examples  of  these  variations  are  shown  in  the 
accompanying  diagrams.  Thus,  of  two  engine 
truck  wheels  illustrated  one  has  a  dished  web,  by 
which  some  yield  is  secured  to  compensate  for  the 
variations  in  the  diameter  of  the  rim  due  to  tempera- 
ture changes,  while  on  the  other  hand  the  wheel 
with  a  straight  web  is  preferred  by  some  motive 
power  departments  for  exactly  the  same  service. 

The  wheel  for  the  Pennsylvania  Railroad  has  a 
rim  2  inches  thick  at  the  outer  face  of  the  tread,  and 
the  web  is  straight  in  section  from  the  bend  at  the 
hub  to  the  bend  under  the  rim.  The  wheel  for  the 
American  Car&  Foundry  Co.  is  thicker  in  the  rim, 
and  the  web  has  a  curved  contour  designed  to  com- 
pensate for  expansion  and  contraction  of  the  rim. 
Again,  in  the  wheel  designed  for  the  Interborough 
Rapid  Transit  Co.  the  thickness  of  the  rim  has  been 
increased  to  3  inches  although  the  diameter  is  but  31 
inches.  This  wheel  also  has  the  curved  contour  web. 

In  electric  service  will  be  found  the  widest  variations 
of  practice.  Street  railways  keep  the  floor  of  the 


car  as  close  to  the  rails  as  possible,  so  as  to  facilitate 
the  entrance  and  exit  of  passengers.  At  the  same 
time  it  is  necessary  to  maintain  a  minimum  diame- 
ter of  wheel  in  order  to  provide  sufficient  clearance 
between  the  street  pavement  and  the  lowest  point 
of  the  motors.  The  thickness  of  the  rim  is  therefore 
determined  by  adding  to  the  minimum  allowable 
radius  of  the  wheel  a  sufficient  thickness  of  metal  to 
raise  the  car  to  the  maximum  height  deemed  advis- 
able, and  this  dimension  represents  the  amount  of 
metal  to  be  worn  away. 

The  wheel  designed  for  the  interurban  cars  of  the 
Cleveland  &  Southwestern  Traction  Co.  is  an 
interesting  example  of  a  compromise  between  the 
M.  C.  B.  standard  wheel  for  steam  roads  and  the 
lighter  wheel  ordinarily  used  in  street  railway  work. 
The  cars  are  heavy  and  the  speed  is  moderately 
high,  necessitating  a  web  and  hub  of  considerable 
strength  and  a  flange  high  enough  to  hold  the  car 
to  the  rails  at  the  speeds  attained  in  the  open  coun- 
try and  yet  low  enough  to  permit  the  wheels  to  pass 
over  the  rails  and  special  work  in  the  city. 


COMPARATIVE     PHYSICAL     AND 
CHEMICAL    TESTS     OF    SOLID 
FORGED  AND    ROLLED    STEEL 
WHEELS,     STEEL    TIRES    AND 
CAST  IRON  WHEELS. 

ALL  the  tires  and  wheels  referred  to  in  this  work 
were  bought  in  the  open  market,  chosen  at  random, 
and  tested  under  identical  conditions  in  comparison 
with  each  other.  They  represent  the  principal  brands 
in  use  giving  satisfactory  service,  and  the  results 
stand  on  the  basis  of  each  sample  representing  the 
average  of  its  class  and  brand.  They  will  be  desig- 
nated as  Tires  A,  B,  C  and  D,  Wheels  E  and  F  and 
Schoen  Wheel. 

Tests  were  made  of  the  tensile  strength,  including 
the  limit  of  elasticity,  per  cent,  of  elongation,  and  the 
reduction  of  area  at  the  point  of  fracture.  The  steels 
were  tested  for  hardness  by  a  drop  of  the  Martel  scale. 
Abrasion  tests  were  made  in  order  to  find  the  resist- 
ance of  the  several  materials  to  grinding  at  various 
points  below  the  tread.  Specimens  were  also  cut 
for  the  determination  of  the  specific  gravity  of  the 
metals  at  different  points  below  the  tread.  Chemi- 
cal analyses  were  made  from  samples  of  each  tire 
and  wheel  taken  from  a  point  below  the  center  of 
the  tread.  Finally,  a  series  of  microphotographs 
were  taken  of  etched  specimens  of  the  metals  in 
order  to  show  their  structure  and  the  relation  of  that 
structure  to  the  physical  and  chemical  properties 
previously  determined  independently. 

The  chemical  analyses  for  carbon  were  all  made 
by  the  combustion  process  and  the  tensile  tests  were 


LOCATION    OF    TENSILE    TEST    SPECIMENS. 

made  in  the  usual  manner,  using  test  pieces  2  inches 
long  between  marks.  The  reason  for  choosing  this 
length  was  that  the  curvature  of  the  treads  of  the 
wheels  and  tires  made  it  impossible  to  cut  longer 
ones.  These  specimens  were  cut  from  the  points  C, 
D,  and  E,  as  indicated  on  the  diagram  showing 
the  location  of  tensile  test  specimens.  These  test 
pieces  were  cut  on  a  chord  of  the  tire  and  gave  an 
available  length  of  2  inches  on  the  reduced  area  J 
inch  in  diameter,  the  center  of  which  was  carefully 
located  at  the  point  indicated  on  the  drawing.  The 
tensile  tests  were  made  in  an  Olsen  testing  machine 
of  100,000  Ibs.  capacity,  and  the  results  obtained  are 
given  in  detail  in  the  following  table  marked  "Com- 
parative Tests  of  Steel  Wheels  and  Tires." 

The    averages    of   these    are    collected   and   pre- 
sented  in  a  condensed  form  in    the   table   marked 


16 


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H 

AVERAGE  OF  COMPARATIVE  TESTS  OF  STEEL  WHEELS 
AND  TIRES. 


Tire  or  Wheel. 


"O'N 


li 


as 


Ill 


Si  . 

il 

s2 

!! 


CTire 

A    " 

D     " 

B     " 

E  Wheel 

F        « 

Schoen  Wheel 


"•35 

20.90 
15.40 

7.40 
14.90 

8.66 


15.89 

"-45 
29.50 

19-33 
6.87 

12.32 


116,761 
I24,0l8 


114,519 
113,610 

"4,477 
124,386 


"3.352 
121,951 
104,095 
107,989 
111,184 
110,857 
121,523 


77.J33 
91,646 
95,008 

82^388 

95.58o 

104,124 


66.06 

73-89 
81.92 
83.18 
72.63 
83-50 
86.45 


818 
817 
783 
799 
872 

875 
1125 


"Average  of  Comparative  Tests  of  Steel  Wheels 
and  Tires." 

From  this  table  it  will  be  seen  that  in  the  wheels  and 
tires  examined  the  average  maximum  tensile  strength 
varied  from  113,610  Ibs.  to  124,386  Ibs.  per  sq.  in. 
of  section;  that  the  elongation  in  2  inches  varied 
from  7.40  per  cent,  to  20.90  per  cent.;  the  limit  of 
elasticity  from  66.06  per  cent,  to  86.45  Per  cent-  of 
the  maximum  tensile  strength;  and  the  hardness 
from  783  to  1125  points  on  the  Martel  Scale. 

In  reviewing  these  results  it  is  necessary  to  con- 
sider the  relative  influence  of  the  chemical  composi- 
tion on  them.  This  is  given  in  the  table  marked 
"  Chemical  Composition  of  Steel  Wheels  and  Tires." 

As  would  be  expected  the  low  carbon  content  of 
the  D  tire  is  accompanied  by  comparatively  low 
tensile  strength,  high  ductility  and  low  hardness. 

At  the  same  time  it  is  evident  that  the  work  put 


CHEMICAL  COMPOSITION    OF   STEEL  WHEELS 
AND  TIRES. 


Wheel. 

Carbon. 

Phos- 
phorus. 

Sulphur. 

Manga- 
nese. 

Silicon. 

C  Tire 

o  616 

o  048 

O  OI  I 

o  698 

O  7O£ 

A     "       

o  716 

O  OCK 

o  023 

O  7  c? 

U.JU^) 

o  26"? 

D     "       

O  <?71 

O  O7  S 

o  0^8 

"•oJ 

O  76"? 

O  COO 

B     "       

y? 

0.676 

U-WS 

o  06  1 

o  oi< 

087^ 

<j.^wy 
O  2  C4 

E  Wheel     

0.646 

O.O7I 

O  O2Q 

0.078 

w>«34 

O  24Q 

F         «        
Schoen  Wheel     .     .     . 

0.631 
0.690 

0.081 
O.OI2 

0.042 
0.000 

0.775 

0.870 

O.24I 
0.094 

on  the  wheel  is  an  influential  factor  in  all  of  these 
results  and  there  is  a  variation  of  tensile  strength 
and  ductility  that  is  not  fully  accounted  for  by  the 
variation  of  carbon  content.  Take  as  an  extreme 
example  the  E  wheel  and  the  Schoen  wheel.  There 
is  a  variation  of  but  .044  per  cent,  in  carbon,  and 
yet  the  maximum  tensile  strength  of  this  E  wheel 
was  but  113,610  Ibs.  per  sq.  in.  while  that  of  the 
Schoen  wheel  was  124,386  Ibs.  with  a  correspond- 
ing elongation  in  2  inches  of  7.40  per  cent,  and 
8.66  per  cent,  respectively,  while  the  limit  of  elas- 
ticity was  72.63  per  cent,  and  86.45  per  cent,  of  the 
tensile  strength  respectively.  The  actual  variation 
in  limit  of  elasticity  was  much  greater,  because  of  the 
higher  base  of  comparison  with  the  Schoen  wheel; 
the  limit  of  elasticity  of  the  E  wheel  being  but  79.12 
per  cent,  of  that  of  the  Schoen  wheel.  In  making 
these  tensile  tests  great  care  was  exercised  not  only 
in  the  preparation  of  the  specimens,  but  in  making  the 
tests  themselves.  The  machine  was  run  slowly  after 
a  stress  of  50,000  Ibs.  had  been  reached,  so  that  the 
limit  of  elasticity  could  be  very  accurately  determined. 


COMPARATIVE   RESULTS   OF   PHYSICAL  TESTS   OF 

SCHOEN   STEEL  WHEELS    WITH   OTHER 

WHEELS   AND   TIRES. 


B 

0 

s 

B 

*Q    Q)    CO 

**H 

& 

*i 

1- 
o  $ 

1 

J*g 

IH 

!l 

Tire  or  Wheel. 

si 

?! 

>£££ 

1^1 

°|1 

pi 

6    a1 

fi  c 

c  ° 

I-S 

*S*§2 

§'1 

*H  ^ 

3 

i 

B 

8 

1 

*l 

Si 

"J 

B 

Schoen  Wheel  .     .     . 

IOO.OO 

I  OO.OO 

IOO.OO 

100.00 

100.00 

100.00 

IOO.OO 

A  Tire      

QQ.7O 

131.06 

02.94 

100.71; 

88.02 

85.47 

72.62 

C      "        

Q7.8? 

128.98 

93.28 

74.08 

76.41 

72.71 

D      «       
B      «        •     .     .     .     . 

93-23 

92.07 

241.34 
177.84 

239-45 
156.90 

85.66 

88.86 

91.25 
91.47 

94.76 

96.22 

69.60 
71.02 

F  Wheel  

Q2.O7 

172.01; 

91.22 

91.79 

96.59 

77.78 

E        " 

QI  74 

8S.4"; 

cc.76 

QI.4Q 

79.12 

84.01 

77.  ci 

A  comparison  of  the  results  obtained  with  all 
wheels  and  tires  with  those  obtained  with  the  Schoen 
steel  wheel  are  given  in  the  table  marked  "Com- 
parative Results  of  Physical  Tests  of  Schoen  Steel 
Wheels  with  Other  Wheels  and  Tires"  in  which  the 
results  obtained  with  the  Schoen  wheel  are  taken 
as  a  base,  and  the  results  obtained  with  the  other 
wheels  and  tires  are  given  in  percentages  of  that  base. 
From  this  table  it  appears  that  the  Schoen  wheel 
leads  all  of  the  others  in  the  items  of  tensile  strength, 
limit  of  elasticity,  per  cent,  of  limit  of  elasticity  to 
ultimate  strength  and  in  hardness. 

The  tests  for  hardness  were  made  with  a  drop 
arranged  with  a  pyramidal  punch.  The  principle 
on  which  this  work  was  done  was  to  measure  the 
force  of  a  blow  delivered  by  the  punch  on  the  smooth 
face  of  the  metal  to  be  tested,  as  well  as  the  amount 


20 


of  metal  displaced  by  the  blow.  This  method  of 
testing  was  devised  by  Col.  J.  T.  Rodman  of  the 
United  States  Army.  It  was  afterwards  developed 
and  formulated  by  Lieut.  Col.  Martel  of  the  French 
army  and  was  then  adopted  as  a  standard  test  by 
the  French  government.  The  results  obtained  are 
known  as  the  degrees  of  hardness  by  the  Martel 
scale.  By  his  investigations  Col.  Martel  showed 
that  the  amount  of  metal  displaced  by  the  punch 
varied  inversely  as  the  hardness  and  directly  as  the 
weight  of  the  drop  and  the  height  of  the  fall. 

In  this  investigation  the  Rodman  pyramidal  punch 
was  used.  It  was  fastened  to  a  drop  weighing,  to- 
gether with  the  punch,  2.2616  kilograms,  and  the 
height  of  fall  was  600  millimeters.  The  punch  was 
of  hardened  tool  steel,  carefully  ground  to  form,  and 
it  withstood  the  work  without  deformation. 

The  specimens  for  the  test  were  cut  from  the  tires 
and  wheels  at  the  same  points  as  the  tensile  test 
pieces  as  indicated  at  C,  D,  and  E,  and  the  results 
obtained  are  given  with  the  other  physical  properties 
in  the  several  tables. 

These  tests  show  the  Schoen  wheel  to  have  been 
the  hardest  of  the  seven  specimens  tested,  and  that 
the  D  tire  was  the  softest.  This  was  to  be  expected 
judging  from  the  carbon  content;  but  we  note  that 
while  the  A  tire  has  a  higher  percentage  of  carbon 
than  the  Schoen  wheel,  for  some  reason  the  latter  is 
the  harder  of  the  two. 

For  the  abrasion  tests  a  cylinder  J  inch  in  diameter 
was  cut  from  a  point  near  the  center  of  the  tread  of 
each  wheel,  extending  vertically  down  into  the  body 
of  the  metal.  This  was  placed  in  a  frame,  with  the 


end  that  was  at  the  tread  resting  on  an  emery 
wheel.  A  load  of  2  Ibs.  nj  oz.  was  put  on  the 
upper  end  of  the  cylinder  to  hold  it  down  on  the 
wheel.  This  weight  was  selected  after  some  pre- 
liminary trials  made  to  ascertain  the  pressure  that 
could  be  used  without  heating  the  material  or  grind- 
ing it  away  too  rapidly  so  as  to  make  the  count 
smaller  than  would  be  convenient  for  making  com- 
parisons. To  this  weight  must  be  added  the  weight 
of  the  cylinders  themselves,  which  varied  about 
0.54  oz.,  a  variation  which  was  duly  considered  and 
the  proper  allowance  made  therefor,  although  it  is 
practically  a  negligible  quantity. 

The  wheel  used  was  made  by  the  Carborundum 
Co.,  and  was  io^9¥  inches  in  diameter  and  f  inch 
thick  when  new.  At  the  conclusion  of  the  tests  the 
wheel  was  worn  to  a  diameter  of  io/¥  inches.  It  was 
known  on  the  maker's  schedule  as  Grit  120;  Grade 
H.,  Bond  G  9.  It  was  run  at  a  speed  of  about 
2,500  revolutions  per  minute. 

While  grinding,  a  constant  and  uniform  stream  of 
water  was  kept  running  on  the  wheel  and  specimen, 
and  at  the  conclusion  of  the  test  the  specimens  were  in- 
variably cool  and  showed  no  signs  of  heating  whatever. 

The  counting  of  the  revolutions  was  done  by  means 
of  a  special  counter  coupled  to  the  shaft  and  having  a 
worm  meshing  with  a  gear  of  25  teeth  mounted  on  a 
shaft  to  which  a  revolution  counter  was  attached.  The 
reading  of  the  counter  was,  therefore,  multiplied  by 
25  to  obtain  the  number  of  revolutions  of  the  wheel. 

In  addition  to  the  regular  tests,  a  cylinder  was 
cut  from  the  same  position  in  a  chilled  cast  iron 
wheel,  and  the  results  of  its  abrasion  test,  as  well  as 


22 


60,000 


DIAGRAM    OF   ABRASION    TESTS    OF   STEEL   TIRES    AND    WHEELS,  SHOWING 

RELATION  OF  RATIO  OF  WEAR  AT  VARIOUS  DEPTHS  BELOW  TREAD 

TO    REVOLUTIONS    OF    EMERY    WHEEL. 


those  of  the  wheels  and  tires,  have  been  plotted  and 
shown  in  the  illustration,  "Diagram  of  Abrasion  Tests 
of  Steel  Tires  and  Wheels."  The  abscissas  indicate  the 
location  of  the  metal  below  the  tread,  and  the  ordinates 
the  number  of  revolutions  of  the  wheel  required  to 
grind  off  J-  inch  from  a  cylinder  J  inch  in  diameter. 
It  will  be  noted  that  in  every  test  there  is  a  rise 
in  the  number  of  revolutions  at  a  point  about  J 
inch  below  the  surface  of  the  tread,  or  for  the  space 
between  J  inch  and  f  inch.  Had  the  work  been 
done  in  rotation  this  peculiarity  might  have  been 
attributed  to  a  change  in  the  texture  of  the  wheel, 
glazing,  heating  the  material,  or  a  similar  cause. 
The  tests  were  started,  however,  before  all  of  the 
cylinders  had  been  finished,  and  those  from  the  A, 
B,  C  and  D  tires  were  well  along  when  a  start  was 
made  with  the  cylinder  cut  from  the  Schoen  wheel. 
This  was  worked  down  in  rotation  with  those  from 
the  tires,  when  that  from  the  E  wheel  was  intro- 
duced, and  this  was  followed  in  the  same  way  by  that 
of  the  F  wheel,  so  that  the  wheel  structure  itself  is 
responsible  for  the  diagram.  By  reducing  these 
diagrams  to  an  average  the  results  are  as  follows: 

AVERAGE  ABRASION   PER  *A  IN.  OF  TIRES  AND  WHEELS. 


Tire  or  Wheel. 

Revolutions. 

Linear  Feet. 

Schoen  Wheel     , 
E  Wheel         .     . 

32.635 

•7Q   66O 

86,483 

C  Tire    .     . 

28  20  C 

01,  ^4^ 

B     "       .... 

26  72O 

/4>/4j 
60  7^8 

F  Wheel     .     . 

2  C  54.O 

67  68  1 

A  Tire    

•3»j^w 

2"?  27O 

6  1  666 

D    "       

21  4.4  C 

Cast  Iron  Wheel     .     . 

5,485 

!4>535 

"* 

Reducing  these  to  percentages  on  the  basis  of  the 
Schoen  Wheel  we  have: 


Tire  or  Wheel 

Per  Cent. 

Schoen  Wheel       

IOO.OO 

E  Wheel       

QI.QC 

C  Tire      

86.42 

B     «                             

8065 

E  Wheel                               

78  26 

A  Tire                              

71.10 

D     "             .               

1    J 

OC.7I 

Cast  Iron  Wheel      

1  6.8  1 

From  this  it  appears  that  the  resistance  of  the 
Schoen  wheel  to  abrasion  was  greater  than  that  of 
any  of  the  other  wheels  and  tires  with  which  it  was 
compared.  The  cast  iron  wheel  gave  the  lowest 
resistance  of  any  cylinder  tested.  The  wheel  was  of 
good  material,  with  a  depth  of  chill  of  about  f  inch. 

An  explanation  of  the  peculiar  rise  in  the  number 
of  revolutions  required  to  grind  these  tires  between 
J  inch  and  f  inch  will  be  brought  out  in  the  dis- 
cussion of  the  microphotographs.  The  examination 
made  of  the  specific  gravities  of  the  metal  of  the 
tires  and  wheels  at  different  points  below  the  surface 
of  the  tread  also  tends  to  show  a  reason  for  the 
peculiar  rise  in  the  rate  of  abrasion  by  the  emery 
wheel.  From  this  examination  it  appears  that  with 
slight  local  aberrations  the  density  of  the  material 
increases  from  the  tread  down  to  a  depth  of  about 
I  inch  and  then  decreases  down  to  2  inches.  A  few 
observations  made  below  these  depths  show  that 
there  is  again  a  tendency  to  increase  in  density  as 
the  inner  edge  of  the  tire  is  approached.  There  was, 


however,  a  variation  of  this  condition  found  in  the 
rim  of  the  Schoen  wheel.  Although  there  was 
a  tendency  to  follow  the  general  behavior  of  the 
other  specimens  it  was  along  a  wavy  line  corre- 
sponding, but  not  in  exact  location,  with  the  variation 
in  the  texture  of  the  grain  which  will  be  brought  out 
in  the  microphotographs  to  be  discussed  later. 

Another  peculiarity  that  was  developed  is  the 
relation  of  hardness,  resistance  to  abrasion  and  ten- 
sile strength  to  the  specific  gravity  of  the  material. 

It  will  be  noted  that  the  rate  of  wear  of  the  cast 
iron  wheel,  as  shown  on  the  diagram,  was  much 
greater  than  that  of  any  of  the  steel  tires  or  wheels. 
The  rapid  fall  in  the  number  of  revolutions  per  J 
inch  of  metal  removed  as  the  chill  was  worn  away  is 
easily  accounted  for,  but  it  was  not  expected  that  the 
variations  from  the  results  obtained  with  the  steel  tires 
would  be  so  great  as  they  were.  In  the  laboratory 
the  metal  and  wheel  were  kept  cool,  so  that  at  no 
time  did  the  temperature  rise,  even  on  the  face  of 
the  specimen,  above  that  of  the  hand.  As  these 
abrasive  tests  have  been  checked  in  other  ways,  as 
will  be  shown  later,  it  appears  that  the  avoidance 
of  heat  is  the  explanation  of  the  great  difference. 

It  must  be  borne  in  mind  that  the  primary  object 
of  these  investigations  was  to  ascertain  to  what  extent 
the  metal  entering  into  the  construction  of  the  Schoen 
wheel  fulfilled  the  requirements  of  actual  service 
as  determined  by  comparison  with  other  wheels 
already  upon  the  market  and  doing  satisfactory  work. 

The  conclusions  to  be  drawn  from  a  general  re- 
view of  the  results  obtained  in  this  investigation  are 
as  follows : 


From  the  physical  tests  of  the  metal  of  the  Schoen 
solid  forged  and  rolled  steel  wheel,  it  appears  that 
it  is  the  strongest  of  any  of  the  tires  and  wheels 
examined.  This  strength  appears  in  the  maximum 
stress  to  which  the  metal  was  subjected,  the  point  at 
which  rupture  took  place  and  the  limit  of  elasticity, 
all  of  which  were  higher  than  in  any  other  wheel  or 
tire,  with  the  single  exception  of  that  of  the  A  tire. 
This  tire  had  a  breaking  load  exceeding  that  of  the 
Schoen  wheel  by  but  428  Ibs.  per  sq.  inch  of  section, 
an  amount  that  is  unimportant. 

The  limit  of  elasticity,  as  expressed  both  in  actual 
figures  and  in  the  percentage  of  the  total  load,  was 
far  higher  in  the  Schoen  wheel  than  in  any  of  the 
others. 

The  ductility  of  the  metal  of  the  Schoen  wheel, 
as  indicated  by  the  elongation  of  the  tensile  test 
pieces,  is  less  than  that  of  any  of  the  other  speci- 
mens with  the  exception  of  the  E  wheel.  Here 
there  is  a  difference  of  nearly  15  per  cent,  in  favor 
of  the  Schoen  wheel,  despite  the  fact  that  the  E 
wheel  contains  nearly  .05  per  cent,  less  carbon. 
This  is  probably  due  to  the  difference  in  the  amount 
of  work  put  on  the  two  wheels. 

In  hardness  the  Schoen  wheel  stands  the  highest 
on  the  scale.  This  is  shown  in  another  way  by  the 
abrasion  tests,  which  show  the  Schoen  wheel  to  be 
the  slowest  of  any  to  grind  away. 

In  specific  gravity  the  Schoen  wheel  is  the  highest. 

The  chemical  composition  is  of  course  a  matter 
that  is  regulated  by  specifications  and  a  review  of 
these  since  the  introduction  of  steel-tired  wheels 
has  shown  a  steady  advance  in  the  carbon  content. 


The  makers  of  the  Schoen  wheel  have  placed 
their  wheel  next  to  the  highest  in  carbon  con- 
tent. This  explains,  in  part,  the  high  ultimate 
tensile  strength,  although  it  cannot  account  for 
it  altogether  because  the  Schoen  wheel  leads  the  A 
tire,  which  has  a  higher  carbon  content,  in  elasticity 
and  maximum  load,  and  in  ductility  is  above  the  E 
wheel  having  a  lower  carbon  content.  In  this  analysis 
special  attention  is  directed  to  the  sulphur,  not  a 
trace  of  which  could  be  found  in  the  Schoen  wheel 
specimens  under  examination. 


M 


ICROGRAPHIC  RECORDS  SHOW- 
ING THE  PENETRATION  OF 
WORK  AND  CHARACTER  OF 
HEAT  TREATMENT. 


THE  physical  properties  of  the  steel  in  these  wheels 
and  tires  having  been  determined,  an  examination 
with  the  microscope  was  made  of  samples  from 
each.  In  the  preparation  of  the  specimens  for  this 
work  strips  were  cut  from  each  wheel  and  tire  in 
accordance  with  the  lines  shown  on  the  diagram. 
The  numbers  1,2,3  an(^  4  are  f°r  tne  identification 
of  the  strips  and  are  used  in  connection  with 
the  photographs,  all  of  which  were  made  with  a 
magnification  of  88  diameters. 


SECTION    OF    TIRE    SHOWING    LINES    OF    LOCATION    OF    MICROPHOTOGRAPHS 


Referring  first  to  the  microphotographs  of  the  D 
tire,  Nos.  I  to  6,  Nos.  I  to  5  were  taken  in  strip 
No.  4,  at  the  tread  and  at  J  inch,  \  inch,  and  I  inch 
below  the  tread  respectively,  and  No.  6  at  I  inch 
below  the  tread  in  strip  No.  3.  These  photographs 
show  an  exceedingly  fine  granular  structure,  indi- 
cating careful  heat  treatment,  a  low  average  per- 
centage of  carbon  and  an  abundance  of  ferrite.  The 
structure  becomes  somewhat  coarser  as  the  metal  is 
penetrated  and  the  normal  structure  is  reached  at 
a  depth  of  about  i  in.  It  will  also  be  seen  that 
there  is  a  slight  difference  between  the  structures  of 
the  metal  as  illustrated  by  the  two  photographs  Nos. 
5  and  6  which  were  taken  at  a  depth  of  i  in.  below 
the  tread  in  strips  4  and  3  respectively.  No.  5  is 
the  finer,  showing  that  the  metal  received  more 
work  at  that  point  than  it  did  deeper  in  on 
strip  No.  3.  This  D  tire  had  the  finest  grain 
and  the  most  uniform  structure  of  the  samples 
examined.  On  the  other  hand,  the  photographs 
corroborate  the  chemical  analysis  of  low  carbon 
content,  possibly  down  to  0.50  per  cent.,  as  indi- 
cated by  the  proportion  of  ferrite  (white)  and 
pearlite  (black). 

Next  in  order  of  fineness  of  grain  comes  the  C,  B 
and  A  tires  respectively.  Here  again  the  relative 
amounts  of  ferrite  and  pearlite  give  an  approximate 
indication  of  the  amount  of  contained  carbon,  from 
which  it  would  appear  that  the  B  and  C  tires  would 
not  run  over  0.60  to  0.65  per  cent,  while  the  A  may 
rise  to  0.70  per  cent, 

The  material  of  the  B  tire  shows  a  practically 
uniform  texture  of  grain  throughout  its  whole  depth, 


AT  EDGE  OF  TREAD. 


No.   2.     %  IN.  BELOW  TREAD. 


No.  5     i  IN.  BELOW  TREAD.  No.  6.     i  IN.  BELOW  TKEAI 

MICROPHOTOGRAPHS    OF    TIRE    D.      88    DIAMETERS. 


No.  9.     %  IN.  BELOW  TREAD.  No.  10.     i  IN.  BELOW  TREAD. 

MICROPHOTOC.'RAFHS    OF    TIRE    C.      88    DIAMETERS. 


33 


with  no  decarbonization  at  the  tread  due  to  heat 
treatment,  although  this  is  undoubtedly  due  to  the 
tire  having  been  turned  before  being  examined. 

In  the  C  tire,  which  was  new,  it  will  be  seen  that 
the  outer  layer  of  the  material  next  to  the  tread,  as 
indicated  by  the  photograph  No.  7,  was  decarbonized 
by  the  action  of  the  heat  treatment  to  which  it  was 
subjected.  The  presence  of  ferrite  is  very  marked 
all  the  way  across  the  tread,  but  below  the  surface, 
as  indicated  by  the  photographs  Nos.  8,  9  and  10, 
which  were  taken  at  depths  of  J  in.,  J  in.,  and  I  in. 
below  the  tread  respectively,  the  grain  assumes  the 
normal  condition  for  the  steel  at  its  finishing  tem- 
perature, although  it  is  somewhat  finer  at  the  edge 
strips  Nos.  I  and  4  than  in  the  center  strips  Nos. 
2  and  3,  indicating  failure  of  the  work  to  penetrate 
the  center. 

The  A  tire  has  such  a  high  carbon  content  that 
the  absence  of  excess  ferrite  causes  the  grain  to  become 
obscure;  it  was  possible  to  bring  the  formation  out  in 
part  only  by  oblique  illumination.  When  viewed 
under  the  microscope  with  the  light  adjusted  to 
the  best  advantage  a  decided  coarsening  of  the  grain 
is  noted  at  successive  points  below  the  tread.  For 
example,  at  the  surface  the  grains  are  apparently  about 
the  same  size  as  those  immediately  below  the  decar- 
bonized shell  of  the  tread  in  the  C  tire,  but  the  grain 
coarsens  rapidly,  and  at  a  depth  of  i  in.  it  is  some- 
what coarser  than  that  of  the  C  tire.  The  structure  is 
interpreted  from  the  microphotographs  in  the  accom- 
panying diagram  made  at  the  same  magnification. 

The  E  wheel  has  an  exceedingly  coarse  structure  with 
traces  throughout  of  inequality  of  carbon  content 


35 


and  disappearance  of  the  grain.  This  is  especially 
noticeable  in  photographs  Nos.  19  and  20  and  ap- 
pears in  the  others  to  a  greater  or  less  extent,  showing 
an  unevenness  of  structure  that  is  suggestive  of  cast 
steel.  This  is  discussed  elsewhere  in  connection 
with  a  shelled-out  wheel  of  the  same  make.  The 
penetration  of  work  was  apparently  very  slight  as  is 
shown  by  the  large  size  of  the  grains  in  No.  17,  taken 
at  the  surface  of  the  tread,  and  the  increasing  size  of 
structure  as  shown  in  Nos.  18,  19  and  20  taken  at 
depths  of  J  in.,  ^  in.,  and  i  in.  respectively. 

The  F  wheel  has  a  coarser  grain  than  the  A,  B  or 
C  tire  and  is  slightly  coarser  than  that  of  the  D  tire. 
The  carbon  content  appears  to  be  about  the  same 
as  that  of  the  C  tire,  or  somewhat  above  0.60,  and 
this  is  checked  by  the  chemical  analysis.  The  sur- 
face decarbonization  which  is  so  marked  in  the  case 
of  the  C  tire  appears  in  this  one  also,  as  indicated 
by  the  increase  of  the  amount  of  ferrite  accom- 
panied by  softening  of  the  surface.  The  large  size 
of  the  grain  in  this  wheel,  as  illustrated  by  photo- 
graphs Nos.  21  to  26,  is  caused  by  the  heat  treat- 
ment to  which  this  wheel  was  subjected.  There  has 
evidently  been  no  work  put  upon  it  after  the  final 
heating.  This  also  explains  why  there  is  compara- 
tively little  enlargement  of  the  grain  going  down 
from  the  surface  of  the  tread.  The  photograph  No. 
21  was  taken  at  the  surface  of  the  tread  and  the  others 
followed  at  depths  of  J  in.,  J  in.,  I  in.,  2|  in.,  and 
2§  in.  respectively. 

The  B  tire  is  typical  of  the  others  and  needs  only 
a  word  of  explanation  of  the  microphotographs  Nos. 
27  to  30,  which  were  taken  at  the  surface  of  the 


No.  15.     y2   IN.  BELOW  TREAD.  No.  16.     i  IN.  BELOW  TREAD. 

MICROPHOTOGRAPHS    OF    TIRE  A.      88    DIAMETERS. 


37 


//v. 


INTERPRETATION  OF  GRAIN  STRUCTURE  IN  TIRE  A  AT  VARYING  DISTANCES 
BELOW    SURFACE    OF    TREAD. 


39 


tread  and  at  depths  of  J  in.,  J  in.,  and  \  in.  re 
spectively.     From  these  the  gradually  increasing  size 
of  the  grain  is  apparent,  though  from  its  large  di- 
mensions, even  at  the  tread,  it  would  appear  that  this 
particular  tire  was  finished  at   a  high  temperature. 

The  microphotographs  of  the  Schoen  wheel  show 
that  for  the  first  J  in.  of  depth  it  has  the  finest 
structure  of  any  of  the  wheels  and  tires  examined, 
but  below  this  depth  its  grain  increases  in  size  in  a 
comparatively  uniform  manner,  though  with  a  varia- 
tion to  be  noted  later.  The  steel  contains  but  a  trace 
of  ferrite,  indicating  that  the  carbon  content  is  about 
the  same  as  that  in  the  A  tire.  Here  again,  owing 
to  the  absence  of  sufficient  ferrite  to  outline  the  grain 
clearly,  it  was  necessary  to  photograph  by  oblique 
illumination,  and  it  was  under  this  light  that  the  ac- 
companying sketches  to  show  the  grain's  size  were 
made.  The  microphotographs  closely  check  the 
abrasion  tests  and  the  determinations  of  specific 
gravity. 

There  are  two  well-defined  zones  in  the  rim  of 
the  Schoen  wheel  that  are  evidently  due  to  the 
rolling.  One  is  at  a  depth  of  J  in.  and  the  other 
f  in.  below  the  surface  of  the  tread.  This  is  best 
illustrated  by  the  accompanying  diagram  of  the 
microstructure  in  the  Schoen  wheel,  in  which  the 
four  strips  and  the  location  of  the  microphotographs 
are  roughly  indicated. 

Strip  No.  I  shows  a  very  fine  grain  at  the  surface 
with  carbon  well  below  0.50  per  cent.  This  structure 
runs  down  for  about  ^  in.,  where  there  begins  a 
gradual  increase  of  the  grain  size  until  the  normal 
dimensions  are  reached  at  about  TV  in.  below  the  top 


No.  19.     %  IN.  BELOW  TREAD.  No.  20.     i  IN.  BELOW  TREAD. 

MICROPHOTOGRAPHS    OF    WHEEL    E.      88    DIAMETERS. 


of  the  flange.  The  first  -fa  in.  is  formed  of  a  very 
fine  mixture  of  about  equal  proportions  of  ferrite 
and  pearlite,  and  below  this  the  ferrite  gradually  dis- 
appears and  the  grains  increase  in  size.  At  a  depth 
of  -YZ  in.  the  ferrite  appears  as  a  discontinuous  band 
or  envelope  around  the  grains  of  pearlite,  indicating 
that  the  carbon  content  is  about  0.70  per  cent.  This 
increase  in  the  size  of  the  grains  continues  down- 
ward until  they  reach  their  maximum  at  a  depth  of 
about  i  in. 

In  strip  No.  2  there  is  the  same  fine-grained  sur- 
face structure  (a)  corresponding  to  that  of  No.  I. 
The  depth  of  this  decreases  from  one  side  of  the 
strip  to  the  other  and  is  about  ^  in.  thick  at  the 
corner.  This  structure  is  shown  in  the  photograph 
No.  31.  On  the  right  hand  side  two  zones  will  be 
seen,  one  of  which,  starting  at  /i,  is  of  very  fine 
pearlite.  The  point  of  maximum  coarseness  is  at  ci. 
This  is  not  really  a  coarse  grain  in  itself,  for  it  is 
fine  even  when  compared  with  that  of  the  D  tire. 
Below  ci  there  is  an  abrupt  change  to  extreme  fine- 
ness again  at  /2.  This  is  followed  by  a  gradual 
increase  in  the  size  of  the  grain  down  to  C2, 
where  the  normal  structure  is  found  at  a  depth  of 
about  i  in. 

In  strip  No.  3  there  is  the  same  fine  grain  at  the 
surface,  as  shown  in  the  photograph  No.  32,  which 
extends  down  to  a  depth  of  about  -^  in.  The  ex- 
treme outside  shows  almost  entire  absence  of  car- 
bon, or  nearly  pure  ferrite.  This  is  followed  by  a 
gradual  increase  in  the  amount  of  carbon  until,  at 
a  depth  of  about  -^  in.,  a  fine  grain  structure  almost 
wholly  of  pearlite  is  indicated  at  fi.  Next  comes  a 


43 


uniform  increase  in  the  size  of  the  grains  until  they 
reach  their  maximum  at  the  point  marked  ci,  where 

there  is  an  abrupt  change  to  a  structure  of  great 
£  i  •  i  •  •  •  & 

fineness  which  in  turn  increases  in  size  to  a  maxi- 
mum at  c2,  when  there  is  a  second  abrupt  change 
to  extreme  fineness  at  /3.  Below  this  there  is  a 
gradual  increase  in  the  grain  size  until  the  normal 
structure  is  reached  at  about  i  in. 

In  strip  No.  4  there  is  the  same  decarbonized  outer 
layer  (a)  which  is  about  ^  in.  thick  at  the  center, 
thickening  towards  the  right  in  the  direction  of  the 
edge  of  the  wheel  rim.  This  structure  differs  in 
appearance  from  the  corresponding  area  in  No.  3, 
due  to  the  distortion  of  the  grain  by  mechanical 
treatment  of  the  metal  after  ferrite  or  pure  iron 
became  excessive  as  the  result  of  burning  out  the 
carbon  on  the  surface  of  the  steel.  The  size  of  the 
grain  increases  from  fine  at  /i,  to  a  maximum  coarse- 
ness at  ci,  J  in.  below  the  surface  where  there  is 
the  same  abrupt  change  as  before  to  a  fine  structure 
at  /2.  This  will  be  seen  by  a  reference  to  photograph 
No.  38.  The  grain  again  increases  to  a  maximum 
coarseness  at  cz,  with  another  change  to  extreme 
fineness  at  /3,  at  a  depth  of  about  |  in.  Beyond 
this  point  the  grain  increases  uniformly  until  the 
normal  size  is  reached  at  a  depth  of  I  in.,  as  indi- 
cated by  photograph  No.  36,  and  the  diagram  of 
grain  sizes. 

These  changes  in  grain  size  are  accounted  for  by 
the  successive  heat  and  mechanical  treatments  to 
which  the  Schoen  wheel  was  subjected. 

The  conclusions  drawn  from  this  work  with  the 
microscope  are  practically  the  same  as  those  reached 


No.  zz.     Y%  IN.  BELOW  TREAD. 


\  '•.  \ 


.  *-< 


No.  23.     %  IN.  BELOW  TREAD 


No    24.     i  IN.  BELOW  TREAD. 


No.  25.    ^l^  IN.  BELOW  TREAD.  No.  26.    2%  IN.  BELOW  TREAD. 

MICROPHOTOGRAPHS    OF    WHEEL    F.      88    DIAMETERS. 


45 


by  a  study  of  the  physical  and  chemical  tests.  It  is 
apparent  that  the  Schoen  wheel  is  quite  equal  to 
the  best  tires,  as  regards  depth  of  finish  and  the 
fineness  of  the  grain  in  the  steel. 


N9I. 


N?2. 


N?3. 


DIAGRAM    ILLUSTRATING    GRAIN    STRUCTURE    OF   SCHOEN    STEEL   WHEEL. 


47 


//Af. 


INTERPRETATION    OF    GRAIN    STRUCTURE    IN    SCHOEN    WHEEL    AT   VARYING 
DISTANCES  BELOW    SURFACE    OF    TREAD. 


No.  29.     %  IN.  BELOW  TREAD.  No.  jo.     %  IN.  BELOW  TREAD. 

MICROPHOTOGRAPHS    OF    TIRE    B.      88    DIAMETERS. 


49 


No.  33.     i/jj  IN.  BELOW  TREAD.  No.  34.     %  IN,  BELOW  TREAD. 

M1CROPHOTOGRAPHS   OF   SCHOEN   STEEL   WHEEL.    88  DIAMETERS. 


51 


No.  37.    AT  OUTER  EDGE  OF  TREAD.  No.  38.    %  IN.  BET.OW  OUTER  EDOE  OF  TREAD. 

MICROPHOTOGRAPHS    OF    SCHOEN    STEEL    WHEEL.     88    DIAMETERS 


53 


T 


HE  SHELLED-OUT  WHEEL. 
A  POSSIBLE  EXPLANATION  OF 
THE  CAUSES  OF  WHEEL  AND 
TIRE  FAILURES. 


THE  service  that  can  be  expected  from  any  wheel 
depends  on  the  soundness  and  homogeneity  of  the 
metal  of  which  it  is  composed.  Irregularity  of  tex- 
ture must  necessarily  result  in  irregular  wear,  while 
local  defects  are  apt  to  result  in  an  immediate  failure. 
Of  such  failures  one  that  is  the  cause  of  much  an- 
noyance and  trouble  is  that  known  as  shelling  out. 
It  was  for  the  purpose  of  ascertaining,  if  possible, 
the  causes  of  this  shelling  out  of  wheels  and  tires 
that  an  examination  with  the  microscope  of  a  num- 
ber of  defective  tires  that  had  failed  in  service  was 
undertaken. 

The  Rules  of  Interchange  of  the  Master  Car  Build- 
ers' Association  define  a  shelled-out  wheel  as  one 
"with  a  defective  tread  on  account  of  pieces  shelling 
out."  This  is  a  poor  definition;  it  may  be  supple- 
mented by  saying  that  the  common  understanding 
of  a  shelled-out  wheel  is  one  in  which  pieces  from 
the  tread  have  flaked  off,  due  to  inherent  defects  in 
the  metal,  such  as  the  laminations  so  frequently 
found  in  wrought  iron  boiler-plates.  It  will  be 
seen  later  that  the  analogy  in  the  case  of  steel  wheels 
is  very  close.  The  cause  of  shelling  out  of  cast 
iron  wheels  is  outside  of  this  investigation  and  will 
not  be  considered. 

The  samples  of  defective  material  investigated 
include  one  of  each  brand  of  wheel  and  tire  pre- 
viously referred  to  in  these  pages,  and  were  obtained 


55 


from  several  railroad  companies.  Each  of  these 
wheels  and  tires  had  one  or  more  shelled-out  spots 
on  the  tread,  and  there  were  also  places  on  each 
where  no  signs  of  shelling  out  could  be  detected. 
The  general  appearance  of  two  samples  is  shown  in 
the  accompanying  photographs,  and  these  may  be 
considered  as  characteristic  of  all. 

A  section  was  taken  at  the  spot  where  the  worst 
shelling  was  found  and  another  through  a  place  on 
the  tread  where  the  metal  showed  no  external  signs 
of  deterioration.  These  sections  were  then  cut  into 
strips  whose  centers  lay  along  the  lines  I,  2,  3,  and 
4  respectively.  (See  page  29.)  The  strips  were  then 
polished,  etched  and  photographed.  The  photo- 
graphs were  taken  at  the  tread,  and  at  intervals 
approximately  J  in.,  J  in.,  f  in.,  and  J  in.  below. 
This  was  not  strictly  followed  in  all  cases,  since  the 
examination  was  governed,  to  a  certain  extent,  by  the 
structure  of  the  material  examined,  as  it  appeared 
under  the  microscope. 

Nos.  39  to  42  show  the  structure  of  the  C  tire  at 
the  point  where  the  worst  shelling  out  occurred.  In 
strip  No.  i,  which  ran  down  into  the  wheel  from  the 
flange,  the  metal  shows  a  fairly  good  fine-grained 
structure  at  the  edge  and  well  down  into  the  rim. 
In  No.  39,  which  was  taken  at  J  in.  below  the  edge, 
spots  of  manganese  sulphide  are  visible.  The  metal 
shows  a  good  structure  in  all  of  the  strips  down  to 
J  in.  in  depth,  wherever  the  photographs  avoid  the 
serious  defects.  In  No.  40,  however,  which  was 
taken  from  strip  No.  3,  there  is  a  distinct  flaw  due 
to  the  presence  of  slag.  The  same  kind  of  flaw 
appears,  very  pronounced,  in  the  photographs  Nos. 


41  and  42,  which  were  taken  from  strips  Nos.  2  and  3 
respectively,  and  through  which  a  continuous  line 
of  slag  extends.  At  other  points  adjacent  to  these 
defective  places  normal  conditions  and  structure  of 
metal  were  found. 

Photographs  Nos.  43  and  44  were  taken  from 
points  on  strip  No.  3,  at  depths  of  J  in.  and  J  in., 
cut  from  an  apparently  solid  piece  of  metal,  and  yet 
they  show  the  presence  of  pronounced  slag  flaws. 
These  flaws  had  not  developed  into  shelled-out  spots, 
but  it  is  reasonable  to  suppose  that  it  was  only  a 
matter  of  time  when  they  would  have  done  so. 

Comparing  this  defective  C  tire  with  the  sound 
new  tire,  the  absence  of  a  decarbonized  surface  on 
the  defective  tire  is  to  be  noticed,  while  it  was  very 
apparent  in  the  new  tire  and  can  be  clearly  seen  in 
photograph  No.  7  (page  33).  This  is  accounted  for 
by  the  fact  that  the  defective  tire  was  in  service  and 
this  soft  outer  shell  had  been  worn  away. 

The  balance  of  the  material  of  the  defective  C 
tire  is  normal  in  structure,  except  that  the  manganese 
sulphide  globules  are  large.  Its  failure  is  readily 
accounted  for  by  the  slag  flaws  found  scattered 
through  the  whole  body  of  the  material  as  shown  in 
Nos.  40  to  44. 

The  B  tire  failed  from  the  same  cause  as  the  C 
tire.  The  structure  of  the  metal  is  normal  through 
a  large  part  of  the  sections,  but  contains  occasional 
slag  cracks,  and  the  characteristic  markings  of  manga- 
nese sulphide,  as  shown  in  No.  45.  In  the  other 
parts  of  the  tire  precisely  the  same  conditions  exist  as 
in  the  C  tire,  namely,  slag  cracks,  as  shown  in  Nos. 
46,  47,  and  48,  which  were  taken  at  various  depths, 


57 


and  where  no  indication  of  shelling  out  had  appeared 
at  the  time  that  the  tire  was  removed  from  service. 
The  presence  of  such  large  slag  veins  as  those  shown 
in  Nos.  46  and  47  leaves  no  room  for  doubt  as  to 
the  cause  of  failure.  The  presence  of  manganese 
sulphide  was  also  indicated  in  the  new  B  tire,  but 
no  slag  veins  are  revealed. 

Nos.  49  and  50  were  taken  from  the  defective  A 
tire.  If  the  metal  of  this  tire  is  compared  with  that 
of  the  sound  new  tire,  it  will  be  seen  that  there  is  no 
variation  in  the  normal  structure  of  the  material  to 
indicate  a  difference  in  the  wearing  quality,  so  that 
the  failure  of  the  shelled-out  tire  is  undoubtedly  due 
to  the  slag  flaws  clearly  shown  in  the  photographs. 

In  the  shelled-out  D  tire  normal  structure  was 
found  but  interspersed  with  slag  cracks  as  in  the 
other  defective  tires.  These  are  shown  in  Nos.  51 
to  54,  some  of  which  were  taken  close  to  the  edge 
of  the  tread.  In  some  places  there  were  spots  of 
manganese  sulphide  near  the  edges,  but  the  cause 
for  failure  is  the  presence  of  the  slag  flaws  that  form 
planes  of  extreme  weakness.  In  photograph  No.  51 
such  a  flaw  is  shown,  which  eventually  must  have 
caused  shelling  out.  Another  example  of  the  same 
sort  is  shown  in  No.  51. 

In  the  E  wheel  the  slag  flaws  can  be  seen  in  Nos. 
55  and  56,  which  were  taken  from  the  shelled-out 
portion.  In  No.  55  there  is  a  distortion  of  the 
slag  defects  due  to  the  forging,  and  in  No.  57  there 
can  be  seen  a  slag  crack  which  existed  in  the  metal 
with  no  visible  defect  on  the  surface. 

The  material  in  this  particular  wheel  is  bad  in  every 
particular.  The  carbon  content  is  low,  apparently 


ranging  from  0.35  to  0.40  per  cent.  The  effect  of 
both  the  work  and  heat  treatment  is  practically  nil  and 
the  structure  looks  like  that  of  untreated  cast  steel  or 
a  metal  that  has  been  overheated.  The  surface  shows 
the  effect  of  cold  rolling  in  the  mixture  of  ferrite  and 
slag,  the  whole  having  a  schistose  appearance.  The 
presence  of  so  much  slag,  as  shown  in  Nos.  55,  56 
and  57,  renders  the  wheel  totally  unfit  for  service. 
The  grain  is  coarse,  as  is  seen  in  photos  Nos.  58  and 
59,  and  resembles  that  in  the  new  wheel  of  the  same 
brand  that  was  examined.  The  carbon  content  of 
the  new  wheel,  however,  was  apparently  much 
higher. 

In  the  shelled-out  portion  of  the  F  wheel  the  slag 
flaws  also  appear  well  down  in  the  metal.  (SeeNos.6i 
and  62.)  What  was  said  of  the  defective  E  wheel 
applies  to  the  F  wheel.  The  carbon  content  seems 
to  be  low,  while  the  presence  of  large  quantities 
of  slag,  photograph  No.  62,  caused  the  many  lines 
of  weakness  along  which  rupture  occurred. 

At  the  time  this  examination  was  being  made  three 
specimens  of  the  Schoen  solid  forged  and  rolled  steel 
wheel  were  obtained,  two  from  shelled-out  wheels  and 
one  from  a  section  of  a  wheel  that  had  been  purposely 
burned  in  heating  during  manufacture.  An  examina- 
tion of  the  photographs  of  the  two  defective  wheels, 
Nos.  67  to  70,  shows  that  there  are  defects  in  the  interior 
of  the  metal  that  were  undoubtedly  the  cause  of  the 
shelling  out,  but  there  is  no  evidence  of  slag.  The 
same  characteristics  are  to  be  noted  in  Nos.  65  and 
66  of  the  specimen  that  had  been  purposely  burned. 
The  three  specimens  are  examples  of  burned  steel 
in  which  there  is  no  evidence  of  slag. 


59 


From  these  photographs  it  is  evident  that  the 
cause  of  the  failure  of  all  of  the  wheels  and  tires, 
except  the  Schoen  wheels,  was  due  to  the  pres- 
ence of  slag  flaws  occurring  near  the  surface  of 
the  tread. 

It  appears,  therefore,  that  there  are  at  least  two 
causes  for  the  shelling  out  of  steel  tires  and  wheels, 
namely,  slag  flaws  and  overheating. 


60 


SHELLED-OUT    STEEL    TIRE    AND    WHEEL; 


6l 


No.  39.     AT  }£  IN.  BELOW  SHELLED  SPOT.  No.  40.     AT  EDGE  OF  SHELLED  SPOT 


No.  41.    SHOWING  SLAG  CRACKS. 


No.  42.     SHOWING  SLAG  CRACKS. 


No.  4j.     ys  IN.  BELOW  TREAD  OF  SOLID  No.  44.     %  IN.  BELOW  TREAD  OF  SOLID 

METAL.  METAL. 

MICROPHOTOGRAPHS    OF   SHELLED-OUT    TIRE    C.      50   DIAMETERS. 


No.  45.     AT 


IN.  BELOW  SHELLED-OUT 
SPOT. 


No.    46.    SLAG  CRACK  IN  SOLID  SECTION 
OF  TIRE. 


No.  48.     MANGANESE  BISULPHIDE  SPOTS. 


No.  47.    SLAG  CRACK  IN  SOLID  PART  OF 
TIRE. 
MICROPHOTOGRAPHS    OF    SHELLED-OUT    TIRE    B. 


No.  49.     AT  EDGE  OF  SHEI.LED-OUT  SPOT. 


No.  50.  SLAG  FLAW  NEAR  EDGE  OF  SOLID 

METAL. 
MICROPHOTOGRAPHS    OF    SHELLED-OUT    TIRE    A. 


No.  51.     SLAG  CRACK  NEAR  EDGE  OF 

SHELLED-OUT    SPOT. 


No.   52.     AT  EDGE  OF  SHELLED-OUT  SPOT. 


No.  53.     SLAG  CRACK  NEAR  EDGE  IN  No.  54.     SLAG  %  IN.  BELOW  TREAD  IN 

SOLID  METAL.  SOLID  METAL. 

MICROPHOTOGRAPHS    OF    SHELLED-OUT    TIRE    D.      50  DIAMETERS. 


No.  55.     AT  EDGE  OF  SHELLED-OUT  SECTION.  No.  56.     Vi«  IN.  BELOW  TREAD  OF  SHELLED- 

orx  SECTION. 


: 


No.  58.     STRUCTURE   %  IN.  BELOW  TREAD 


No.  57.     SLAG  AT  EDGE  OF  SOLID  METAL. 


No.  59.    STRUCTURE  AT  EDGE  OF  TREAD.  No.  60.     SLAG  AT  CENTER  OF  TREAD. 

MICROPHOTOGRAPHS    OF   SHELLED-OUT    WHEEL    E.     50   DIAMETERS. 


69 


No.  63.    STRUCTURE  %  IN.  BELOW  TKEAD.  No.  64.     STRUCTURE  yz  IN.  BELOW  TREAD. 

M1CROPHOTOCRAPHS    OF    SHELLED-OUT    WHEEL    F.       50    DIAMETERS. 


No.  69.  No.  70. 

MICROPHOTOGRAPHS    OF  .BURNED    METAL    OF   SCHOEN    STEEL    WHEEL. 
50   DIAMETERS. 


73 


BURNED    METAL    OF   SCHOEN    STEEL   WHEEL 


75 


s 


OME  AREAS  OF  CONTACT  BE- 
TWEEN WHEELS  OF  VARIOUS 
DIAMETERS  UNDER  LOADS  AND 
THE  RAIL. 


THE  mutual  compression  between  the  wheel  and 
the  rail  when  under  a  load  has  an  important  bearing 
on  the  durability  of  both  and  also  on  the  adhesion  of 
the  wheels  when  used  as  drivers.  The  investigation 
was  made  with  various  types  of  cars  and  locomotives 
to  determine:  the  area  of  contact  between  the  wheel 
and  the  rail;  the  average  pressure  exerted  per  square 
inch  over  this  area;  the  accumulated  pressure  at 
the  center  of  this  area;  the  yield  of  the  metal  in  both 
the  rail  and  the  wheel  under  the  imposed  load;  the 
relative  action  of  the  wheel  and  the  rail  under  load; 
the  comparative  action  of  wheels  of  different  diam- 
eters, and  the  comparative  action  of  steel  and  cast 
iron  wheels. 

Through  the  courtesy  of  Mr.  J.  F.  Deems,  General 
S.  M.  P.  of  the  New  York  Central  Lines,  the  pre- 
liminary work  involving  the  use  of  cars  and  loco- 
motives was  done  at  the  West  Albany  yards  of  the 
New  York  Central  &  Hudson  River  R.R.  A  concrete 
pier  was  built  under  one  of  the  rails  of  a  level  piece 
of  track  to  secure  a  firm  foundation.  A  section 
about  10  in.  long  was  cut  out  of  the  rail  and  a 
short  piece  with  perfect  contour  was  inserted  on 
top  of  the  pier.  The  car  or  locomotive  under 
which  a  wheel  was  to  be  examined  was  run 
over  this  short  section  of  rail  and  one  wheel 
allowed  to  rest  upon  it.  The  wheel  was  then 
raised  with  its  mate  so  that  the  section  could  be 


77 


removed  and  the  top  smeared  with  a  thin  coating 
of  red  lead.  The  piece  of  rail  was  then  replaced 
and  the  wheel  lowered  upon  it  with  its  whole  load. 
This  made  a  spot  on  the  red  lead  the  size  of 
the  area  of  contact  of  the  wheel  and  the  rail. 
The  wheel  was  again  raised,  the  section  of  the 
rail  removed,  and  the  area  of  contact,  as  indicated 
by  the  spot  on  the  red  lead,  transferred  to 
tracing  cloth.  The  rail  was  again  smeared  and 
replaced,  and  the  wheel  was  turned  through 
one  quarter  of  a  revolution  and  the  work 
repeated. 

In  the  supplementary  work  in  the  laboratory  a 
section  of  a  yS-in.  tire,  a  section  of  a  steel  wheel  and 
a  section  of  a  cast  iron  wheel  were  used.  One  of 
these  sections  was  fastened  to  the  plunger  of  the 
testing  machine  and  was  raised  and  lowered  on  the 
heads  of  short  sections  of  rails  resting  on  the  platen 
of  the  same.  The  size  and  shape  of  the  contact 
area  was  obtained  by  the  interposition  between  the 
tire  and  rail  section  of  a  piece  of  white  tissue  paper 
resting  on  a  sheet  of  carbon  paper  which  made 
the  imprint  on  the  white  paper. 

The  tests  at  West  Albany  were  made  with  three 
cars  and  two  locomotives.  In  all  32  contacts  were 
obtained,  and  plaster  of  Paris  casts  were  taken  of 
the  treads  of  the  wheels  at  all  points  at  which  the 
contact  areas  were  obtained.  Some  of  the  wheels 
were  new,  while  others  were  partly  worn,  a  condition 
that  evidently  had  much  to  do  with  the  shape  and 
size  of  the  spot. 

These  areas  were  carefully  measured  with  a 
planimeter  and  gave  the  following  average  results: 


Wheels  Used  Under. 

Total  Weight 
on  Wheels 
in  Lbs. 

Average  of 
Area  Contact. 

Average  Weight 
per  Sq.  In.  of 
Area  in  Lbs. 

Cafe  Car  (35  in.)      .... 

6,075 

•2325 

28,700 

Gondola  (33  in.)      .     .     .     . 

M.575 

•3775 

40,100 

Consolidation  Driver  (63  in.) 

17,325 

•335° 

52,080 

Atlantic  Driver  (78  in.)    .     . 

19.995 

.6325 

31,820 

Atlantic  Trailer  (485/ie  in.)  . 

19,210 

•4725 

44,400 

Dining  Car  (34^5  in.).     .     . 

9.4I5 

.2600 

37^70 

In  these  tests  the  influence  of  weight  and  diameter 
is  partially  illustrated.  The  two  wheels  of  the  At- 
lantic engine,  for  example,  carry  about  the  same 
weight.  The  areas  of  contact  are  nearly  in  an  in- 
verse ratio  to  the  diameters.  Comparing  the  wheels 
of  the  cafe  and  dining  cars,  the  wheel  with  the 
heavier  load  has  much  the  greater  weight  per  sq.  in. 
of  area,  showing  that  the  metal  does  not  yield  in 
direct  proportion  to  the  weight,  at  least  within  the 
limits  of  the  loads  here  imposed. 

In  the  laboratory  the  first  series  of  tests  made  was 
to  apply  pressures,  increasing  by  small  increments, 
to  the  tread  of  a  36-in.  steel  wheel  resting  on  an  8o-lb. 
rail.  The  lowest  load  applied  was  500  Ibs.  This 
was  increased  by  increments  of  500  Ibs.  up  to 


123  4 

CONTACTS   OF   35-IN.    STEEL-TIRED    WHEEL   UNDER    CAFE    CAR. 
WEIGHT    ON    WHEEL,  6,075   LBS. 


79 


CONTACTS    OF   3&-INCH    WORN    CAST    IRON    WHEEL    UNDER    GONDOLA    CAR. 
WEIGHT    ON    WHEEL,  14,575    LBS. 


1  2 

CONTACTS  OF  78-IN.  STEEL-TIRED    DRIVING  WHEEL,  ATLANTIC 
LOCOMOTIVE.      WEIGHT    ON    WHEEL,  19,995    LBS. 

20,000  Ibs.;  then  by  increments  of  1,000  Ibs.  up  to 
30,000  Ibs. 

The  second  series  was  made  with  the  same  wheel 
resting  on  a  loo-lb.  rail,  starting  at  a  load  of  500  Ibs. 
and  increasing  by  increments  of  500  Ibs.  up  to  2,000 
Ibs;  then  by  increments  of  1,000  Ibs.  up  to  10,000 
Ibs.;  then  by  increments  of  2,000  Ibs.  up  to  30,000  Ibs. 

The  third  series  was  made  with  a  j8-in.  tire  on  an 
8o-lb.  rail,  starting  at  500  Ibs.  and  then  increasing 
by  increments  of  500  Ibs.  to  2,000  Ibs.;  then  by 


.2 

CONTACTS  OF  48%6-IN.  STEEL-TIRED  TRAILER  TRUCK  WHEEL,  ATLANTIC 
LOCOMOTIVE.     WEIGHT  ON  WHEEL,  19,210  LBS. 

increments  of  1,000  Ibs.  to  8,000  Ibs.;  then  by  2,000 
Ibs.  to  30,000  Ibs.  and  from  that  point  by  increments 
of  2,500  Ibs.  to  40,000  Ibs. 

The  fourth  series  was  made  with  the  78-in.  tire  on 
a  loo-lb.  rail,  starting  at  500  Ibs.  and  increasing  by 
increments  of  500  Ibs.  to  2,000  Ibs. ;  then  by  1 ,000  Ibs. 
to  8,000  Ibs.;  then  by  2,000  Ibs.  to  30,000  Ibs.,  and 
finally  by  2,500  Ibs.  to  35,000  Ibs. 

The  fifth  series  was  made  with  the  section  of  a 
cast  iron  wheel  33  ins.  in  diameter.  This  was  tested 
on  a  loo-lb.  rail  only,  starting  at  500  Ibs.;  increasing 
by  500  Ibs.  increments  to  20,000  Ibs.;  then  by  1,000 
Ibs.  to  30,000  Ibs.;  then  by  2,500  Ibs.  to  40,000  Ibs.; 
then  by  5,000  Ibs.  to  150,000  Ibs. 

The  sixth  series  was  made  with  a  36-in.  steel 
wheel  on  a  loo-lb.  rail,  and  started  at  a  load  of 
50,000  Ibs.  which  was  increased  by  increments  of 
10,000  Ibs.  to  150,000  Ibs. 

The  results  obtained  from  these  tests  have  been 
plotted  on  the  accompanying  diagram  and  average 
lines  drawn  which  show  the  accumulated  pressure 
per  sq.  in.  of  area  under  the  actual  loads  imposed, 
the  lines  being  an  average  of  the  results  obtained. 
It  will  be  seen,  on  comparing  the  lines  of  the  36-in. 
steel  wheel  and  of  the  33-in.  cast  iron  wheel,  that 
there  is  comparatively  little  difference  up  to  a  load 


81 


500  Lbs. 

Av.  Pressure  per 
Sq. In. 7  143  Lbs. 
Area  .07  Sq.  In. 


«* 


5,000  Lbs. 

Av.  Pressure  per 

Sql In. 62, 500  Lbs. 

Area  .08  Sq.  In. 


10,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  100,000  Lbs. 

Area  .10  Sq.  In. 


* 

15,000  Lbs. 

AV.  Pressure  per 

Sq.  In.  100,000  Lbs. 

Area  .15  Sq.  In. 


20,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  86.956  Lbs. 

Area  .23  Sq.  In. 


25,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  92, 555  Lbs. 

Area  .27  Sq.  In. 


30,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  96,774  Lbs. 

Area  .31   Sq. In. 


CONTACTS    BETWEEN   36-IN.    STEEL-TIRED    WHEEL    AND   80-LB.    RAIL. 


500  Lbs. 

Av.  Pressure  per 

Sq.  In.  16,666  Lbs. 

Area  .03  Sq.  In. 


5,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  62.500  Lbs. 

Area  .08  Sq.  In. 


10,000  Lbs. 

Av.  Pressure  per 

Sq. In. 71, 428  Lbs. 

Area  .14  Sq.  In. 


16,000  Lbs 

Av.  Pressure  per 

Sq.  In   94,1 17  Lbs. 

Area    17  Sq    In. 


20,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  105,263  Lbs. 

Area  .19  Sq.  In. 


26,000  Lbs. 

Av    Pressure  per 

Sq.  In.  108,333  Lbs. 

Area  .24  Sq.  In. 


30,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  11 5,384  Lbs. 

Area  .26  Sq.  In. 


CONTACTS    BETWEEN   36-IN.    STEEL-TIRED    WHEEL   AND   lOO^LB.    RAIL. 


500  Lbs. 

Av    Pressure  per 

Sq.  in.  25  000  Lb*. 

Area   02  Sq   In 


5,000  Lbs 

Av.  Pressure  per 

Sq.  In.  62,500  Lba/ 

Area  .08  Sq.  In. 


10,000  Lbs. 

Av   Pressure  per 

Sq   In   71,428  Lbs. 

Area    14  Sq. m 


16000  Lbs. 

Av   Pressure  per 

Sq    In   80,000  Lbs 

Area    20  Sq    In 


20,000  Lbs. 

Av    Pressure  p«r 

Sq.  In.  90, 909  L fas'. 

Area  .22  Sq   In. 


26,000  {.£*. 

Av.  Pressure  per 

Sq.  In    100,000  Lbs. 

Area  .26  Sq.  in. 


30,000  Lbs. 

Av  Pressure  per 

Sq.  In    100,000  Lbs. 

Area   SO  Sq   In 


85,000  Lbs. 

Av..  Pressure  per 

fl,  In,  102,941  J.b». 

Area  .34  Sq    In 


40,000  Lbs 

Av.  Pressure  per 

6q.  In.  111,111  Lb« 

Area   36  Sq.  In 


CONTACTS   BETWEEN  78-IN.   STEEL-TIRED  WHEEL   AND   80-LB.    RAIL. 


500  Lbs. 

Av.  Pressure  per 

Sq   In   16,666  Lbs. 

Area  .03  84.  In. 


10,000  Lbs. 

Av,  Pressure  per 

Sq.  In  83  333  Lbs 

Area   12  8q   In. 


16,000  Lbs. 

Av    Pressure  per 

Sq.  In.  106,666  Lb» 

Area    '5Sq    In. 


20,000  Lbs 

Av    Pressure  per 

Sq    In    105,263  Lbs 

Area   19  Sq   In 


26,000  Lbs. 

Av.  Pressure  per 

5a    In.  100,000  Lb». 

Area  .26  84.  In. 


30,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  103,448  Lbs. 

Area  .29  Sq.  In. 


85,000  Lbs 

Av   Pressure  per 

Sq.  In,  109,376  Lbe 

Area  .32  Sq    In 


CONTACTS  BETWEEN  78-IN.   STEEL-TIRED    WHEEL   AND   JOO-LB.    RAIL. 


50,000  Lbs. 

Av.  Pressure  per 

•Sq. In. 131,578  Lba. 

"Area  .38  Sq.  Jn. 


60,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  127,659  Lbs 

Area  .47  Sa.  In. 


70,000  Lbs. 

Av.  Pressure  per 

Sq.  In   129,629  Lbs. 

Area  .54  Sq.  In. 


80,000  Lbs. 

Av.  Pressure  per 

Sq.  In,  137,288  Lbs. 

Area  .59  Sq.  In. 


90,000  Lbs. 

Av    Pressure  per 

Sq.  In.  135,757  Lbs. 

Area  .66  Sq.  In 


100,000  Lbs 

Av   Pressure  per 

Sq.  ln.J38,888  Lb* 

Area'  72  Sq.  In 


11 0,000  Lbs. 

AV.  Pressure  per 

Sq.  In.  137,500  Lbs 

Area  .80  Sq.  In. 


120,000  Lbs. 

Av    Pressure  per 

Sq    In,  141,176  Lbs 

Area  .85  Sq.  In 


CONTACTS    BETWEEN   36-IN.    STEEL   WHEEL    AND   100-LB.    RAIL.£ 

of  22,500  Ibs.,  after  which  the  load  per  sq.  in.  increases 
more  rapidly  with  the  cast  iron  wheel  than  with  the 
steel  wheel.  At  a  load  of  37,500  Ibs.  there  is  a 
marked  breaking  down  of  the  metal  in  the  cast  iron 


130,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  141 ,304  Lbs 

Area  .92  Sq.  In. 


140,000  Lbs. 

Av.  Pressure  per 

Sq.  In    137,254  Lbs. 

Area  1.02Sq.  In. 


150,000  Lbs. 

Av.  Pressure  per 

Sq   In.  144  230  Lbs. 

Area  1.04  S«j,  In. 

CONTACTS   BETWEEN   36-IN.    STEEL   WHEEL    AND    100-LB.    RAIL. 

wheel  showing  that  the  crushing  strength  has  been 
exceeded. 

A  tentative  explanation  of  this  phenomenon  is 
that  the  hard  chilled  cast  iron  wheel  is  practically 
unyielding  and  that,  when  the  load  is  imposed,  the 
whole  of  the  compression  takes  place  in  the  rail.  The 
area  of  contact  is  small  and  the  average  pressure  per 
sq.  in.  of  area  is  high.  The  yield  in  the  rail  holds, 
for  a  time,  against  the  increasing  load,  thus  cutting 
down  the  size  of  the  area  between  22,500  Ibs.  and 
40,000  Ibs.  The  wheel  itself  then  takes  a  permanent 
set,  increasing  the  area  of  contact  very  rapidly  and 
lowering  the  average.  In  the  case  of  the  steel  wheel, 
yielding  takes  place  in  both  the  wheel  and  the  rail, 


500  Lbs. 

Av.  Pressure  per 
Sq.  In.  9,090  Lbs. 
Area  .055  Sq.  In. 


1  •* 


1,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  14,285  Lbs. 

Area  .07  Sq.  In. 


2,500  Lbs. 
Av.  Pressure  per 
Sq.  In.  33,333  Lbs. 
Area  .075  Sq.  In. 


3,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  43,750  Lbs. 

Area  .08  Sq.  In. 


4,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  50,000  Lbs. 

Area  .09  Sq.  In. 


6,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  54,545  Lbs. 

Area  .11  Sq. In. 


10,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  83,333  Lbs. 

Area  .12  Sq. In. 


11, 500  Lbs. 

Av.  Pressure  per 

Sq.  In.  88,461  Lbs. 

Area  .13  Sq.  In. 


13,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  96,428  Lbs. 

Area  .14  Sq.  In. 


14,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  96.666  Lbs 

Area  .15  Sq.  In. 


15,000  Lbs. 

Av.  Pr'esaure  per 

Sq.  In   93,750  Lbs 

Area  .16  Sq.  In. 


16,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  97,058  Lbs. 

Area  .17  Sq.  In. 


17,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  94.444  Lbs. 

Area  .18  Sq.  In. 


19,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  100,000  Lbs, 

Area. 19  Sq.  In. 


25,000  Lbs. 

Av.  Pressure  per 

Sq    In   125,000  Lbs» 

Area  .20  Sq.  in. 


27,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  128,571  Lbs. 

Area  .21  Sq.  In. 


28,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  127,272  Lbs. 

Area  .22  Sq   In. 


30,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  130,434  Lbs. 

Area  .23  Sq.  In. 


32,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  130,000  Lbs. 

Area  ,25  Sq.  In. 


35,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  134,615  Lbs. 

Area  .26  Sq.  In. 


CONTACTS    BETWEEN   33-IN.    CAST   IRON    WHEEL    AND    100-LB.    RAIL. 


86 


with  the  result  that  an  equilibrium  is  established  on 
a  smaller  area  and  the  actual  breaking  down  of  the 
metal  occurs  under  a  higher  pressure. 

In  the  case  of  the  cast  iron  wheel  it  will  be 
noted  that  the  curve  of  average  pressure  shows  a 
break  and  yield  of  the  material  at  a  load  of  27,000 
Ibs.,  though  it  rises  again  and  makes  a  second  com- 
plete break  at  37,500  Ibs.,  from  which  there  is  no 
recovery.  In  the  case  of  the  steel  wheel  the  break- 
down does  not  occur  until  a  load  of  50,000  Ibs.  is 
reached,  and  even  then  there  is  a  gradual  and  prac- 
tically uniform  advance  to  150,000  Ibs. 

In  the  tests  of  both  the  cast  iron  wheel  and  the 
steel  wheel,  the  permanent  set  was  all  in  the  rail. 
Both  wheels  were  carefully  examined  with  a  micro- 
scope after  the  load  of  150,000  Ibs.  had  been  imposed 
and  the  tests  were  completed,  and  no  appearance 
of  yielding  or  cracking  of  either  could  be  detected. 
The  rail,  on  the  other  hand,  showed  signs  of  a  perma- 
nent set  under  a  load  of  20,000  Ibs.,  and  this  set 
increased  with  the  increasing  loads.  The  rail  was 
examined  immediately  after  applying  loads  of  12,000, 
15,000,  25,000,  30,000,  35,000,  and  40,000  Ibs.  The 
spot  or  depression  left  by  the  wheel  could  be  seen 
after  the  20,000  Ibs.  load  had  been  imposed,  but  not 
before. 

The  difference  between  the  areas  of  contact  of  the 
wheels  under  cars  and  locomotives  and  the  wheels 
tested  in  the  laboratory,  in  which  the  area  was 
larger,  is  probably  due  to  the  fact  that  the  wheels 
under  the  cars  and  locomotives  were  worn  somewhat 
hollow  and  so  fitted  the  rail  head  to  a  greater  extent. 
In  service,  however,  the  swinging  of  the  wheels  from 


.87 


37,500  Lbs. 

Av.  Pressure  per 

Sq.  In.  138,888  Lbs. 

Area  .27  Sq.  In. 


40,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  137,777  Lbs. 

Area  .29  Sq.  In. 


45,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  136,363  Lbs. 

Area  .33  Sq.  In. 


50,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  121,951  Lbs. 

Area  .41  Sq.  In. 


55,000  Lbs. 

Av..  Pressure  per 

Sq. Jn.  119.565  Lbs. 

Area  .46  Sq:  In. 


59,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  118,000  Lbs. 

Area  .50  Sq.  In. 


65,000  Lbs. 

Av.  Pressure  per 

Sq. In.  118  181Lbs. 

Area  .55  Sq.  In. 


70,000  Lbs. 

Av.  Pressure  per 

Sq. In. 118,644  Lbs. 

Area  .59  Sq.  In. 


75,000  L'bs. 

Av.  Pressure  per 

Sq    In.  122,950  Lbs. 

Area  .61  Sq.  In. 


CONTACTS   BETWEEN   33-IN.   CAST    IRON    WHEEL   AND    100-LB.    RAIL. 


88: 


80,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  126,983  Lbs. 

Area  .63  Sq.  In. 


85,000  Lbs. 

Av.  Pressure  per 

Sq. In. 116,666  Lbs 

Area  .72  Sq.  In. 


90,000  Lbs. 

Av    Pressure  per 

Sq.  In.  121, 621  Lba. 

Area  .74  Sq.  In. 


95,000  Lbs 

Av.  Pressure  per 

Sq.  In.  121,794  Lbs. 

Area    78  Sq.  In. 


100,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  120,481  Lbs. 

Area  .83  Sq.  In. 


105,000  Lbs. 

Av.  Pressure  pot 

Sq.  In.  117,977  Lbs. 

Area  .89  Sq   In. 


110,000  Lbs. 

Av.  Pressure  per. 

Sq.  In.  118,279  Lbs. 

Area  .93  Sq.  In. 


11 5,000  Lbs. 

Av.  Pressure  per- 

Sq.  In.  116,161  Lbs. 

Area  .99  Sq.  In. 


120,000  Lbs. 

Av.  Pressure  per 

Sq    In.  115,384  Lbs. 

Area  1.04  Sq.  In. 


CONTACTS   BETWEEN   33-IN.    CAST    IRON    WHEEL    AND    100-LB.    RAIL. 


89 


125,000  Lbs. 

AV.  Pressure  per 

Sq.  In.  119.047  Lbs. 

Area  1.05  Sq.  In. 


130,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  117,117  Lbs. 

Area  1.11  Sq. In. 


135,000  Lbs. 

Av.  Pressure  per 

Sq. In. 119,469  Lbs. 

Area  1.13Sq.  In. 


140,000  Lbs. 

Av.  Pressure  per 

Sq.  In.  130,434  Lbs. 

Area  1.15  Sq.  In. 


CONTACTS   BETWEEN   33-IN.    CAST   IRON    WHEEL    AND    100-LB.    RAIL. 

one  side  of  the  track  to  the  other  brings  the  projec- 
tions on  the  outer  edge  of  the  rim  against  the  rail, 
undoubtedly  causing  a  much  higher  load  to  be  put 
on  a  smaller  area  of  contact  than  was  applied  in  the 
laboratory. 

The  permanent  set  taken  by  the  rail  at  so  low  a 
load    as    20,000    Ibs.    raised    the    question    of  the 


maximum  pressure  imposed  at  the  center  of  the  area 
of  contact.  It  was  assumed  that  when  the  wheel 
first  touched  the  rail  the  area  of  contact  would  be  a 
mathematical  point  if  both  surfaces  were  perfectly 
smooth  and  true.  As  the  load  is  increased  the 
metal  in  both  the  wheel  and  rail  yields  and  the  area 
of  contact  increases.  This  increase  is  from  the  center 
out  to  the  edge,  and  the  pressure  per  unit  of  area  is 
evidently  at  a  maximum  at  the  center  and  decreases 
to  nothing  at  the  edge.  In  order  to  estimate  approx- 
imately the  maximum  pressure  it  was  assumed  that 
the  metal  in  the  area  on  which  a  load  had  once  been 
imposed  always  sustained  it,  and  by  building  up 
from  the  center  by  increments  the  final  load  was  at- 
tained. Take  the  case  of  the  36-in.  steel-tired  wheel 
on  the  loo-lb.  rail.  An  area  of  .03  sq.  in.  sustained  the 
initial  load  of  500  Ibs.,  with  an  average  pressure  of 
1 6,666  Ibs.  per  sq.  in.  By  increasing  this  load  to  5,000 
Ibs.  the  area  is  increased  to  .08  sq.  in.  If  this  extra 
4,500  Ibs.  which  was  applied  be  considered  as  loaded 
uniformly  over  the  whole  area,  there  would  be  an 
average  increase  of  pressure  of  56,250  Ibs.  per  sq.  in. 
or  56,250+16,666  =  72,916  Ibs.  per  sq.  in.  on  the 
original  .03  sq.  in.  which  carried  the  initial  load  of 
500  Ibs.  This  assumption  runs  the  load  up  to  an 
exceedingly  high  limit,  possibly  too  high,  as  it  gives 
a  pressure  of  more  than  170,000  Ibs.  per  sq.  in.  at  the 
center  of  the  area  of  contact,  with  a  load  of  20,000  Ibs. 
In  considering  the  results  obtained  in  this  investi- 
gation, it  must  be  borne  in  mind  that  the  areas  of 
contact  were  all  obtained  under  static  loads.  Run- 
ning conditions  must  necessarily  be  more  severe 
and  impose  higher  stresses.  In  an  investigation 


145,000  Lbs. 

Av   Pressure  per 

Sq.  In.  123,931  Lbs. 

Area  1.17  Sq.  In. 


150, 000  Lbs. 

Av.  Pressure  per 

Sq.  In.  124,049  Lbs. 

Area  1.21  Sq.  In. 


CONTACTS   BETWEEN   33-IN.    CAST    IRON    WHEEL    AND    100-LB.    RAIL. 

conducted  several  years  ago  it  was  found  that  the 
stresses  in  truck  and  body  bolsters,  while  a  car  is  in 
motion,  are  from  20  to  50  per  cent,  more  than  the 
stresses  due  to  static  loads  alone.  If  this  is  true  for  parts 
located  above  the  springs,  there  must  certainly  be  an 
equal  or  greater  increase  at  the  point  of  contact  be- 
tween the  wheel  and  the  rail.  Then,  too,  the  blows 
received  from  passing  over  low  joints  or  worn  frogs, 
will  raise  the  pressure  between  the  wheel  and  the 
rail  to  a  point  which  the  tests  under  static  loads  have 
shown  to  be  excessive.  For  example,  the  wheels, 
under  a  car  of  100,000  Ibs.  capacity  with  a  10  per 
cent,  overload,  carry  an  approximate  static  load  of 
18,750  Ibs.  each.  A  drop  of  yV  in.  is  equivalent  to  a 
blow  of  about  97  foot  Ibs.  If  the  drop  is  checked  by 
a  yield  in  the  rail  of  three-eighths  of  the  amount  of 
the  drop  (yf  *  in.)  the  pressure  on  the  rail  will  amount 
to  50,000  Ibs.  This  is  certainly  excessive. 

Comparing  the  steel  and  cast  iron  wheels,  it  ap- 
pears that  no  damage  was  done  to  either  wheel  under 


LOAD  //V  POUA/DS 


DIAGRAM    SHOWING    THE    RELATION    BETWEEN    WEIGHTS    ON    WHEELS,   AND 
THAT  ON  THE  AREA  OF  CONTACT  BETWEEN  THE  WHEEL  AND  THE  RAIL. 

a  static  load  of  150,000  Ibs.  If  the  two  wheels  are 
subjected  to  the  pounding  action  of  service,  however, 
the  result  cannot  fail  to  be  the  earlier  disintegration 
of  the  harder,  more  unyielding  and  more  brittle 
material.  Exact  comparative  data  along  this  line 
are  not  yet  available. 


93 


The  conclusions  to  be  drawn  from  this  part  of 
the  work  may  be  summed  up  as  follows : 

The  average  pressure  imposed  on  the  metal  of  the 
wheel  and  rail  is  within  safe  limits  at  low  loads,  but 
when  a  load  of  20,000  Ibs.  is  reached  the  elastic  limit 
of  the  metal  is  passed  and  a  permanent  set  appears 
in  the  rail. 

The  accumulated  pressure  at  the  center  of  the  area 
of  contact  is  excessive  at  comparatively  small  loads, 
and  is  only  prevented  from  doing  injury  by  the  support 
of  the  surrounding  metal.  How  far  this  compression 
extends  into  the  body  of  the  two  pieces  of  metal  in 
contact  is  not  known,  but  presumably  it  extends  down 
to  the  base  of  the  rail  and  into  the  hub  of  the  wheel. 

Under  a  static  load  the  rail  yields  first,  owing, 
probably,  to  the  fact  that  the  metal  of  the  surface  of 
the  head  of  the  rail  is  not  as  well  supported  by  the 
metal  below  as  in  the  case  of  the  wheel. 

The  effect  of  difference  of  diameter  in  wheels  carry- 
ing the  same  load  is  insignificant  and  is  only  appreci- 
able when  the  difference  is  great.  Hence  it  is  imma- 
terial so  far  as  stresses  on  the  wheel  or  rail  are 
concerned,  whether  small  or  large  wheels,  within  the 
limits  of  practice,  are  used. 

A  hard,  unyielding  cast  iron  wheel  inflicts  more 
damage  on  the  rail  than  a  steel  wheel,  and  the  wear 
of  the  rail  will  be  greater  with  the  cast  iron  wheels 
than  with  the  steel  wheels. 

It  is  probable  that  the  reason  why  the  damage 
that  would  be  expected  from  heavy  wheel  loads  in 
service  does  not  immediately  appear,  is  that  the  rail, 
by  bending  under  the  passing  wheel,  increases  the 
area  of  contact  and  thus  relieves  the  surface  stresses. 


94 


c 


COEFFICIENTS  OF  FRICTION  BE- 
TWEEN WHEELS  AND  RAILS. 
TRACTIVE  VALUES.  SKIDDING 
AND  SLIPPING. 


THE  resistance  of  a  wheel  to  slipping  on  the  rail 
depends  upon  two  causes  frequently  confused,  but 
which  are  to  be  considered  separately.  These  are 
friction  and  abrasion. 

Frictional  resistance  is  due  to  the  roughnesses  of 
the  two  surfaces  in  contact,  and  may  be  compared  to 
the  lifting  of  the  weight  to  be  moved  over  the  suc- 
cessive inequalities  of  the  surface  on  which  it  rests. 
Abrasion,  on  the  other  hand,  involves  the  removal 
or  cutting  away  of  the  particles  of  the  masses  in 
contact.  The  slipping  of  a  wheel,  such  as  would 
produce  a  flat  spot,  involves  both  frictional  resist- 
ance and  abrasion.  If  there  was  no  slipping  of 
the  wheel  on  the  rail  there  would  be  no  wear,  pro- 
vided the  rolling  action  did  not  produce  sufficient 
pressure  on  any  one  point  to  crush  the  metal  or 
cause  it  to  flow.  But  there  is  always  more  or  less 
slip  even  on  a  straight  line. 

There  are  two  kinds  of  slipping  to  which  car 
wheels  may  be  subjected.  One  is  the  skidding 
action  due  to  the  locking  of  the  wheels  by  the  brake- 
shoes.  The  other  form  occurs  when  the  driving 
wheels  of  electric  motor  cars,  for  instance,  are  turned 
faster  than  the  corresponding  rate  of  motion  of  the 
car  and  the  whole  periphery  of  the  wheel  slides 
over  the  rail.  In  order  to  determine  whether  the 
resistances  to  these  two  kinds  of  slipping  were  the 
same  certain  experiments  were  made. 


95 


ARRANGEMENT    OF    APPARATUS    TO    TEST    THE    FRICTIONAL    RESISTANCE    OF 
CAR    WHEELS    TO    SKIDDING. 

The  apparatus  was  designed  to  produce,  as  nearly 
as  possible,  the  actual  conditions  of  track  work. 

Two  pieces  of  steel  rails  of  75  Ibs.  section,  one  of 
which  had  been  worn  smooth  in  service,  the  other  a 
piece  of  new  rail,  together  with  a  section  of  a  steel 
wheel  and  a  section  of  a  cast  iron  wheel,  with  the 
treads  of  both  smooth  and  free  from  imperfections, 
were  used  for  the  tests.  The  testing  machines  were 
made  by  Tinius  Olsen  &  Co.,  one  with  a  capacity  of 
100,000  Ibs.  and  the  other  a  capacity  of  50,000  Ibs. 

The  apparatus  is  shown  in  the  accompanying 
illustrations  for  the  skidding  movement.  The  wheel 
section  was  set  on  the  rail  and  loaded  by  the  100,000 
Ibs.  capacity  machine.  It  was  then  slipped  over  the 
rail  by  a  pull  on  the  connection  rod  reaching  to 
the  other  machine  which  measured  the  amount  of 
the  pull  required  to  slip  the  wheel  on  the  rail. 


96 


Y/w//////////^^^^ 


TfSTMC  AMCHM£ 

ARRANGEMENT    OF   APPARATUS    FOR    TESTING    THE    FRICTIONAL    RESISTANCE 
OF    CAR    WHEELS    TO    SPINNING. 

In  loading  the  wheel,  the  pressure  was  applied 
through  a  plate  resting  on  two  rollers.  In  this  way 
the  friction,  except  that  between  the  wheel  and  the 
rail,  was  reduced  to  practically  nothing. 

For  the  spinning  motion,  the  bearing  plate  above 
the  rollers  was  made  convex  and  the  bottom  plate 
resting  on  the  top  of  the  wheel  was  made  concave, 
both  surfaces  being  concentric  with  the  tread  of  the 
wheel.  A  pull  on  the  wheel,  therefore,  caused  it  to 
roll  under  the  bearing  plate  as  though  it  were  re- 
volving on  its  own  center.  The  arrangement  of  this 
is  clearly  shown  in  the  diagram. 

The  force  required  to  move  the  wheel  on  the  rail 
was  weighed  by  a  bell  crank  with  a  knife-edge  bear- 
ing, resting  on  a  heavy  casting  attached  to  the  bed 


97 


plate  of  the  small  testing  machine.  The  vertical  arm 
was  attached  to  the  pull  rod  and  the  end  of  the 
horizontal  arm  had  a  bearing  on  a  wedge  or  knife 
edge  that  was  forced  down  by  the  platen  of  the 
machine. 

The  wheel  section  was  placed  in  position  on  the  rail 
and  weighted  with  a  predetermined  load.  Pressure 
was  then  applied  to  the  wedge  on  the  small  machine. 
This  pressure  was  transferred  through  the  bell  crank 
as  a  pull  on  the  connecting  rod.  When  slipping 
occurred,  the  event  was  marked  instantly  by  the  drop 
of  the  beam  of  the  small  machine.  The  movement  of 
the  wheel  over  the  rail  usually  amounted  to  about 
-fa  in.  As  the  object  of  the  investigation  was  to 
determine  the  friction  at  rest  no  attempt  was  made 
to  measure  the  pull  after  the  first  slip  occurred. 
This  was  markedly  less  than  that  required  to  start 
the  movement  from  a  state  of  rest. 

Separate  tests  were  made  with  steel  and  cast 
iron  wheels  on  the  old  and  new  rails,  for  both  the 
skidding  and  spinning  motions.  In  loading  the 
wheels,  the  weights  were  increased  by  regular  incre- 
ments of  2,000  Ibs.  up  to  30,000  Ibs.  Three  tests 
were  made  with  each  loading  and  for  each  condition 
of  wheel  movement.  The  average  of  the  three  tests 
in  each  case  is  given  in  the  accompanying  table. 

There  was  so  little  difference  in  the  pull  required 
to  slip  the  wheels  on  the  old  and  new  rails  that  an 
average  of  the  results  obtained  is  given  as  the  resist- 
ance to  spinning  and  skidding  of  the  two  wheels  on 
a  steel  rail. 

The  table  shows  that  the  resistance  to  spinning  of 
the  steel  wheel  is  somewhat  greater  than  that  of  the 


COEFFICIENTS    OF   FRICTION    BETWEEN   WHEELS 
AND   RAILS. 


Kind  of  Motion 

Load  on  Wheel 

Spinning 

Skidding 

Steel 

Cast  Iron 

Steel 

Cast  Iron 

Wheel. 

Wheel. 

Wheel. 

Wheel. 

2,000 

•259 

•243 

.285 

.287 

4,000 

.240 

.215 

.254 

.259 

6,000 

•234 

.208 

.245 

.254 

8,000 

.228 

.206 

.246 

.242 

10,000 

.215 

.204 

.238 

•233 

1  2,000 

.212 

.205 

•237 

.223 

14,000 

.207 

.199 

•233 

.226 

16,000 

.204 

.I96 

.232 

.219 

18,000 

.204 

.I98 

.231 

.2I9 

20,000 

.201 

.194 

.236 

.220 

22,000 

.205 

.191 

.238 

.223 

24,000 

.204 

.192 

•235 

.224 

26,OOO 

.205 

189 

.232 

.223 

28,OOO 

.203 

.186 

.236 

.217 

3O,OOO 

.203 

.183 

•234 

.214 

cast  iron  wheel,  a  fact  which  is  brought  out  more 
forcibly  in  the  table  of  coefficients  of  friction,  in 
which  the  coefficient  of  the  steel  wheel  is  invariably 
higher  than  that  of  the  cast  iron. 

It  also  appears  from  this  table  that  the  coefficient 
of  friction  of  the  steel  wheel  decreases  as  the  load  is 
increased,  up  to  a  pressure  of  about  15,000  Ibs.,  after 
which  it  is  practically  constant.  The  coefficient  of 
friction  of  the  cast  iron  wheel  decreases  rather  rapidly, 
like  that  of  the  steel  wheel,  up  to  a  load  of  15,000 
Ibs.,  after  which  it  falls  away  slowly,  though  a 
tendency  to  decrease  with  the  increase  of  load  is 
manifest. 

As  regards  skidding,  the  values  of  the  coefficients 
of  the  two  wheels  bear  the  same  relation  to  each  other 


99 


as  they  do  for  spinning.     The  coefficient  of  resistance 
is  greater  for  the  steel  wheel  than  for  the  cast  iron 
wheel,  and  there  is  the  same  falling  off  in  the  value 
of  the  coefficient  as  the  load  is  increased  up  to  about 
15,000  Ibs.,  after  which  that  of  the  steel  wheel  is 
nearly  constant,  while  that  of  the  cast  iron  wheel 
continues  to  fall  away  slowly.     It  would  be  difficult 
to  explain  these  phenomena  without  the  data  ob- 
tained  in    the    investigations    previously    described, 
made  to  determine  the  area  of  contact  between  the 
wheel  and  the  rail,  and  the  relative  rate  of  abrasion 
of  the  steel  and  cast  iron  wheels  on  the  emery  wheel. 
The  results  of  those  investigations  also  serve  to  ex- 
plain why  the  coefficient  for  a  skidding  wheel  is 
higher  than  the  coefficient  for  a  wheel  that  is  spinning. 
In  the  case  of  the  cast  iron  wheel,  it  was  shown  in 
the  preceding  chapter  that  the  imposition  of  a  heavy 
load  caused  a  breaking  down  of  the  metal  in  the 
rail  at  a  certain  point,  while  no  such  failure  occurred 
with  the  steel  wheel  under  the  same  load.     The  cast 
iron  wheel  being  rigid,  inelastic  and  incompressible 
on  the  tread,  was  forced  down  into  the  metal  of  the 
rail,  causing  the  rail  to  do  all  of  the  yielding  needed 
to  produce  the  area  of  contact  obtained,  with  the 
result  that  it  was  soon  compressed  beyond  its  elastic 
limit  and  given  a  permanent  set.     The  steel  wheel 
yielded  as  well  as  the  rail,  thus  relieving  the  rail  of 
a  part  of  its  compression  and  increasing  the  area  of 
contact.     This  behavior  of  the  two  wheels  explains 
in  part  the  results  obtained  in  these  tests.     In  ad- 
dition, it  must  be  remembered  that  the  normal  co- 
efficient of  friction  is  greater  between  steel  and  steel 
than  it  is  between  cast  iron  and  steel. 


When  the  cast  iron  wheel  is  loaded  on  the  rail  it 
indents  the  rail,  in  proportion  to  the  pressure  ap- 
plied, without  being  distorted  itself.  If,  then,  it  is 
turned,  as  by  a  motor,  it  simply  revolves  in  the  concave 
depression  in  the  rail,  without  undergoing  any  de- 
formation itself  and  with  no  resistance  other  than 
that  of  overcoming  the  friction  between  the  surfaces 
of  the  wheel  and  rail.  The  steel  wheel,  on  the 
other  hand,  is  itself  compressed  as  well  as  the  rail, 
so  that  when  it  is  turned  a  continuous  progressive 
compression  of  the  tread  is  set  up,  equal  to  the 
amount  of  the  original  compression.  Hence,  the 
resistance  to  turning  will  be  equal  to  the  frictional 
resistance  plus  that  set  up  by  this  compression. 

It  was  shown  that  the  cast  iron  wheel  was  cut 
away  much  more  rapidly  under  the  emery  wheel 
than  were  the  steel  tires  and  wheels.  In  the  tests 
for  skidding,  the  loads  were  successively  applied 
without  readjusting  the  wheel  on  the  rail,  with 
the  result  that  the  steel  wheel  was  skidded  about 
ij  in.  and  the  cast  iron  wheel  about  I  in.  This 
was  done  under  loads  increasing  from  2,000  Ibs. 
up  to  30,000  Ibs.  Under  this  treatment  the  steel 
wheel  developed  a  slid-flat  spot  about  -f$  in.  long, 
and  the  cast  iron  wheel  a  spot  about  |  in.  long.  In 
both  cases  the  rail  was  spotted  and  the  metal  was 
rolled  up  in  folds,  indicating  the  direction  of  the 
motion  of  the  wheel.  The  piece  of  rail  used  with 
the  steel  wheel  was  spotted  for  a  distance  of  about 
if  in.,  while  the  piece  used  with  the  cast  iron  wheel 
was  spotted  for  a  length  of  about  i\  in.  This 
abrasion  of  the  cast  iron  wheel  probably  accounts 
for  the  lower  resistance  to  skidding  as  compared  with 


101 


the  steel  wheel.  For  the  same  weight  and  for  the 
same  distance  of  skidding,  the  amount  of  metal 
abraded  from  the  cast  iron  wheel  was  in  almost 
exactly  the  same  ratio  to  that  removed  from  the  steel 
wheel,  as  is  shown  in  the  diagram  of  abrasion  tests. 

It  will  be  remembered  that,  for  the  lower  wheel 
loads,  the  investigation  of  contact  areas  showed  that 
there  was  comparatively  little  difference  between  the 
areas  obtained  with  cast  iron  wheels  and  with  steel 
wheels,  and  that  it  was  inferred  that  the  total  com- 
pression of  the  metal  was  approximately  the  same 
in  both  cases.  Under  these  circumstances  it  would 
be  expected  that,  if  the  power  required  to  distort  the 
metal  of  a  steel  rail  and  tire  were  the  same,  the 
resistance  to  skidding  of  the  steel  wheel  and  the  cast 
iron  wheel  would  also  be  the  same.  But,  owing  to 
the  more  rapid  abrasion  of  the  cast  iron  wheel,  as 
soon  as  it  begins  to  skid  it  wears,  and  by  thus  in- 
creasing the  area  of  contact  it  lessens  the  depression 
of  the  rail,  decreases  the  amount  of  metal  to  be 
distorted,  lowers  the  resistance  to  the  motion,  and 
makes  the  coefficient  of  friction  of  skidding  less  on 
the  cast  iron  wheel  than  on  the  steel  wheel. 

This  depression  of  the  rail  due  to  the  imposition  of 
the  wheel  load  accounts  for  the  higher  coefficient  of 
friction  obtained  with  a  skidding  wheel  than  with  a 
spinning  wheel.  With  a  wheel  spinning  there  is  no 
continuous  deformation  of  the  metal  of  the  rail  to  be 
effected.  In  skidding  there  is  a  depression  of  the 
rail  to  be  carried  forward  like  a  wave,  which  natural- 
ly raises  the  resistance  and  makes  the  coefficient 
greater  than  where  slipping  over  one  spot  alone 
takes  place. 


102 


While  it  is  not  safe  to  draw  rigid  conclusions  from 
the  limited  amount  of  data  obtained,  it  does  appear 
that  inasmuch  as  the  steel  wheel  offers  greater  re- 
sistance to  spinning  it  is  better  adapted  for  use  as  the 
driving  wheel  of  an  electric  car  than  the  cast  iron 
wheel;  and  further,  its  higher  coefficient  of  friction 
renders  it  less  liable  to  skidding. 

This  matter  of  wheels  skidding,  with  the  conse- 
quent development  of  flat  spots  on  the  tread,  was 
considered  of  enough  importance  to  warrant  further 
investigation. 

It  has  been  noted  by  many  other  investigators 
that  steel  wheels  do  not  flatten  as  readily  as  cast  iron 
wheels.  By  some  this  is  attributed  to  the  fact  that 
small  flat  spots  once  formed  on  the  tread  of  a  steel 
wheel  may  be  rolled  out,  whereas  they  have  a  tend- 
ency to  grow  larger  on  cast  iron  wheels.  The 
abrasion  and  skidding  tests  which  have  been  made 
seem  to  show,  however,  that  it  is  the  lower  resistance 
to  grinding  of  the  cast  iron  wheel  that  accounts  for 
the  more  rapid  development  of  these  flat  spots. 

To  briefly  recapitulate,  these  tests  showed  that  the 
rate  of  grinding  of  the  first  J  in.  below  the  tread  was 
about  4.64  times  as  fast  in  the  cast  iron  wheel 
as  in  the  Schoen  steel  wheel.  For  the  second 
J  in.  the  ratio  became  6.37  and  for  the  third  |  in. 
15.93,  showing  the  rapid  decrease  of  wearing  resist- 
ance of  the  cast  iron  wheel  below  the  surface.  In 
the  skidding  tests  in  the  laboratory  the  effects  were 
confined  to  the  metal  close  to  the  surface,  and  it 
was  found  that,  with  the  same  amount  of  skidding, 
the  amount  of  metal  removed  was  about  5.12  times 
as  great  on  the  cast  iron  wheel  as  on  the  steel  wheel. 


103 


A  further  check  on  these  figures  was  afterwards  ob- 
tained by  taking  the  time  required  to  remove  approxi- 
mately the  same  amount  of  material  from  the  treads 
of  cast  iron  and  steel  wheels  in  a  wheel  grinding 
machine.  It  was  found  that  it  took  from  four  to 
five  times  as  long  to  grind  down  the  steel  wheels  as 
it  did  to  grind  the  cast  iron  wheels.  In  all  of  the 
foregoing  investigations  the  metal  of  the  wheel  under 
test  was  kept  cool,  either  by  a  stream  of  water 
or  by  doing  the  work  so  slowly  that  natural  radia- 
tion counteracted  the  tendency  to  heat,  and  the 
temperature  of  the  metal  was  not  raised  above  100 
deg.  Fahr. 

For  the  purpose  of  ascertaining  whether  the  re- 
sults of  these  investigations  were  comparable  with 
the  results  obtained  in  actual  railroad  service,  when 
the  wheels  were  locked  and  skidded  under  a  car, 
series  of  tests  were  made  by  skidding  the  wheels 
under  a  loaded  car. 

Through  the  courtesy  of  the  New  York,  Ontario 
&  Western  Railroad  a  piece  of  track  and  a  suitable  box 
car  were  supplied  for  the  tests.  One  pair  of  wheels 
and  axle  were  removed  from  under  the  car,  and 
replaced  by  an  axle  on  which  a  Schoen  steel  wheel 
and  a  new  cast  iron  wheel  had  been  pressed.  These 
wheels  were  33^  in.  and  33  in.  in  diameter,  respect- 
ively. This  pair  of  wheels  was  placed  at  the  end  of 
the  car,  and  was  fitted  with  two  brake-beams,  so  that 
twice  the  usual  brake-shoe  pressure  could  be  applied 
on  the  wheels.  By  this  means  the  wheels  could 
be  held  in  a  fixed  position  throughout  a  run.  But 
it  was  more  difficult  to  hold  the  wheels  at  low  speed 
than  at  high  speed. 


104 


The  car  was  loaded  until  the  weight  on  the  pair  of 
wheels  to  be  tested  was  exactly  24,000  Ibs.  The  car 
was  then  hauled  back  and  forth  over  a  piece  of  track 
1,850  ft.  long.  The  brake  was  set  and  the  wheels  skid- 
ded for  the  whole  distance.  The  car  was  hauled  at 
two  speeds,  namely,  three  and  twelve  miles  an  hour. 

When  the  car  was  hauled  at  a  speed  of  three  miles 
an  hour,  flat  spots  were  made  on  the  steel  wheel  about 
.30  sq.  in.  in  area,  while  the  spots  formed  on  the  cast 
iron  wheel  were  .80  sq.  in.  in  area.  These  areas 
correspond  to  diameters  of  about  f  in.  and  i  in. 
respectively,  though  the  spots  on  the  cast  iron  wheel 
were  elongated  to  about  if  in.,  which  indicated  some- 
what more  metal  removed.  The  volume  of  metal 
abraded  from  the  cast  iron  wheel  was  about  5!  times 
greater  than  that  from  the  steel  wheel. 

While  the  movement  was  slow  the  wheels  remained 
cool.  But  when  the  speed  was  increased  to  twelve 
miles  an  hour  heating  took  place  and  the  cutting 
was  more  rapid  on  the  steel  wheel. 

For  the  first  1,850  ft.  run  the  areas  of  the  flat  spots 
produced  at  a  speed  of  12  miles  an  hour  averaged 
8.125  scl-  ms>  on  tne  steel  wheel  and  4.445  s(l-  ms-  on 
the  cast  iron  wheel.  The  estimated  amount  of 
metal  worn  away  was  4.63  times  as  much  with  the 
steel  wheel  as  with  the  cast  iron  wheel. 

When  the  skidding  was  continued  the  rate  of  wear 
increased  very  rapidly  with  the  cast  iron  wheel,  while 
there  was  little  increase  with  the  steel  wheel.  At 
the  end  of  the  run  of  3,700  ft.  the  area  of  the  flat 
spot  on  the  steel  wheel  was  8.43  sq.  ins.,  an  increase 
of  .305  sq.  in.,  while  the  area  of  the  spot  on  the  cast 
iron  wheel  was  5.72  sq.  ins.,  an  increase  of  1.275  sq.  m- 


105 


From  this  it  appears  that  the  cast  iron  wheel  wore 
away  more  rapidly  than  the  steel  wheel  after  the 
hard  surface  metal  had  been  broken  through. 

The  indications  are  that  in  skidding  a  short  dis- 
tance at  low  speed  a  cast  iron  wheel  is  more  apt  to 
develop  a  flat  spot  than  is  a  steel  wheel.  On  the 
other  hand,  if  the  skidding  continues  for  some  dis- 
tance at  a  high  speed,  the  wheel  becomes  heated  and 
then  the  steel  wheel  is  the  first  to  yield,  unless  the 
surface  chill  of  the  cast  iron  wheel  has  already  been 
worn  through. 


106 


ATERAL    THRUST     OP    WHEELS 
AGAINST    THE    RAILS.      BREAK 
ING     STRESSES     OF     WHEEL 
FLANGES. 

IT  is  generally  admitted  that  cast  iron  wheels  under 
high  capacity  cars  are  giving  unsatisfactory  service 
and,  because  of  their  inherent  lack  of  strength,  are 
a  source  of  danger.  Prior  to  1905  little  was  known 
of  the  strength  of  these  wheels  except  that  they  had 
a  shorter  life  and  gave  far  more  trouble  from  flange 
breakage  under  the  high  capacity  cars  than  they 
had  under  cars  with  a  capacity  of  only  60,000  Ibs. 
In  that  year  Professor  Goss  made  some  tests  in 
the  laboratory  of  Purdue  University  to  ascertain 
the  strength  of  the  flanges  of  cast  iron  wheels. 

Six  new  wheels  and  one  wheel  which  had  broken 
in  service  were  tested.  The  wheel  to  be  tested  was 


APPARATUS    FOR    TESTING    STRENGTH    OF   WHEEL   FLANGES. 


107 


TABLE  OF   BREAKING  STRESSES    OF  WHEEL  FLANGES. 


No. 
of 
Test 

Breaking 
Load. 
Lbs. 

No.  of  Wheel. 

Point  of  Application 
of  Load. 

Remarks. 

I 

52,850 

M.  C.  B.  19413 

Between  brackets 

2 

47.75° 

« 

Opposite         " 

3 

49,35° 

« 

Between          " 

4 

53»4°o 

« 

Opposite         " 

5 

62,850 

M.  C.  B.  19410 

Between          " 

6 

48,700 

a 

Opposite         " 

7 

58,250 

ti 

Between         " 

8 

58,000 

a 

Opposite        " 

9 

74,850 

M.  C.  B.  19254 

Between         " 

10 

72,200 

« 

Opposite        " 

ii 

87,000 

" 

Between          " 

12 

68,550 

« 

Opposite         " 

X3 

99,300 

(e)  650  Ibs. 

Between         " 

14 

100,000 

« 

Opposite         " 

15 

105,900 

« 

Between         " 

16 

68,200 

«« 

Opposite         " 

f  Wheel 

11 

79»35° 
52.3oo 

J9558 

«                 « 
Between           « 

1  broke 
I  through 
l_rim. 

in 

111,600 

(f  )  700  Ibs.  Tape  I 

Opposite         « 

*9 

87,000 

t< 

Between           ' 

20 

109,900 

« 

Opposite          ' 

21 

22 

98,900 

M(  1904  M.  C.  B.    ) 
(s)  1  700  Ibs.  Tape  2  J 

K                                 <« 

23 

98,900 

(i 

il                                 l« 

mounted  on  a  strong  mandrel  secured  to  the  base 
of  the  testing  machine  in  such  a  manner  that  it  could 
not  slip,  and  a  punch  was  forced  down  against  the 
flange  in  the  same  way  that  the  rail  presses  against 
it  in  service.  Pressure  was  applied  until  the  flange 
broke.  The  general  arrangement  of  the  apparatus 
is  shown  in  the  illustration  on  page  107.  The  punch 
A  was  bolted  to  the  head  of  the  machine.  It  was 
prevented  from  springing  away  from  the  work  by 
a  roller  bearing  against  a  bracket  which  was  bolted 
to  the  platen  of  the  machine. 


108 


AVERAGES  OF  BREAKING  STRESSES  OF  WHEEL 
FLANGES. 


Average  Breaking 
Load.    Libs. 

No.  of  Wheel. 

Remarks. 

5°,837 

19,413 

Taken  from  service 

56,95° 

19,410 

«          «<          « 

75,65° 
52,3°° 

19,254 
19,558 

Broken  wheel  taken 
from  service. 

Three  of  the  wheels  tested,  Nos.  19,413,  19,410 
and  19,254,  were  new  wheels  of  M.  C.  B.  dimen- 
sions. The  fourth,  No.  19,558,  was  a  piece  of  a 
wheel  which  had  broken  in  service.  In  addition  to 
these  specimens  three  new  wheels  were  tested  which 
were  especially  designed  to  give  increased  flange 
strength.  These  were  marked 

(e)  650  IBs. 

(f)  700  Ibs.  Tape  i 

(g)  700  Ibs.      "     2 

Wheels  (e)  and  (f )  were  of  a  reinforced  flange  design 
and  wheel  (g)  was  the  then  proposed  Standard  of 
the  M.  C.  B.  Association  with  reinforced  flange. 

Four  tests  were  made  with  each  of  the  M.  C.  B. 
standard  wheels,  and  from  two  to  four  tests  with 
each  of  the  others.  The  results  are  given  in  detail 
in  the  Table  of  Breaking  Stresses  of  Wheel  Flanges. 

Three  of  the  tests  made  on  the  (e)  wheel  showed  a 
flange  strength  of  approximately  100,000  Ibs.,  while 
the  fourth  test  (16)  gave  only  68,200  Ibs.  In  view 
of  this  wide  difference  an  attempt  was  made  to  get 
a  fifth  test  from  this  wheel  by  applying  pressure 
to  the  flange  midway  between  two  of  the  breaks 


109 


previously  made,  with  the  result  that  the  wheel  broke 
through  the  rim  at  79,350  Ibs. 

Test  No.  1 8  was  made  on  a  piece  of  a  wheel 
which  had  broken  in  service  and  the  holding  device 
which  had  been  employed  for  new  wheels  had  to 
be  supplemented  by  additional  clamping  for  the 
test.  For  this  reason  it  is  not  known  whether  the 
results  obtained  from  the  fragments  are  entirely  com- 
parable with  those  obtained  from  the  whole  wheels. 

It  will  be  seen  from  these  tests  that  not  only  were 
there  wide  variations  in  the  strength  of  flanges  of 
wheels  of  similar  design  but  in  different  parts  of 
the  flange  of  the  same  wheel.  Reinforcing  the  flange 
added  to  the  strength,  but  even  in  individual  wheels 
thus  reinforced  there  is  a  variation  from  68,200  Ibs. 
to  105,900  Ibs.  in  the  breaking  strength. 

These  tests  cover  practically  all  that  is  known  of 
the  strength  of  the  cast  iron  wheel  to  resist  the 
thrust  on  the  rail.  In  order  to  ascertain  approxi- 
mately the  relative  strength  of  the  steel  wheel  under 
similar  conditions  a  Schoen  wheel  was  tested  in 
the  same  way.  The  work  was  done  under  a  power- 
ful hydraulic  press  and  the  flange  broke  off  under  a 
load  of  526,612  Ibs.  This  was  more  than  4.7  times 
the  load  required  to  break  the  strongest  part  of  the 
reinforced  flange  and  more  than  1 1  times  the  load  re- 
quired to  break  the  weakest  of  the  standard  flanges. 

The  ratio  of  4.7  to  I  corresponds  fairly  closely 
with  the  ratio  of  the  tensile  strength  of  the  two 
metals.  It  has  been  seen  that  the  tensile  strength 
of  the  steel  of  the  Schoen  wheel  is  about  124,000 
Ibs.  In  some  tests  of  cast  iron  that  have  been  made 
it  was  found  that  samples  of  gray  iron  made  from 


no 


TRACK    APPARATUS    FOR    ASCERTAINING    WHEEL    AND    RAIL    PRESSURES. 


Ill 


first-class  wheel  mixtures  broke  at  from  16,000  Ibs. 
to  17,000  Ibs,  while  test  specimens,  carefully  ground 
from  the  white  chilled  iron  of  a  car  wheel,  broke 
under  loads  as  high  as  36,000  Ibs. 

The  lack  of  any  data  on  the  stresses  to  which 
wheels  are  subjected  in  service,  other  than  that 
based  on  theoretical  calculations,  necessitated  the 
carrying  out  of  a  series  of  investigations  which 
would  throw  some  light  on  the  subject  from  a  practi- 
cal standpoint.  The  object  was  to  determine  the 
lateral  thrust  to  which  the  wheels  under  high  capac- 
ity freight  cars  may  be  subjected  when  moving  over 
curves  at  different  speeds,  and,  if  possible,  to  develop 
the  law  in  accordance  with  which  the  thrust  in- 
creases as  the  speed  of  the  car  is  increased. 

As  an  investigation  of  this  kind  had  never  before 
been  undertaken,  it  was  necessary  to  design  and 
build  a  special  piece  of  apparatus. 

The  device  as  a  whole  may  be  divided  into  two  parts : 
the  track  apparatus  and  the  recording  instrument. 

The  track  apparatus  consisted  of  a  section  of  rail 
3  ft.  long  held  in  position  in  the  track  and  free  to 
move  outward  by  an  amount  sufficient  to  exert  a 
pressure  on  a  hydraulic  cylinder  in  proportion  to 
the  lateral  thrust  against  it. 

The  recording  instrument  was  set  on  a  small  table 
placed  about  7  ft.  from  the  track  and  was  connected 
with  the  cylinder  of  the  track  apparatus  by  a  J-in. 
brass  pipe.  It  consisted  of  an  ordinary  pressure  gauge, 
having  a  maximum  registration  of  200  Ibs.  per  sq.  in., 
a  recording  pressure  gauge  and  a  pressure  pump  by 
which  an  initial  pressure  could  be  put  on  the  whole 
system  of  piping.  The  ordinary  pressure  gauge  was 


113 


S  f£*  HOUR 


~&  PCRHOUR 


*.   £.-• 


JD47  IBLE&  FEJ*  HOUR 
SAMPLES  OP  SPEED  K.ECBTKAT1OKS. 

one  made  by  the  Utka  Steam  Gauge  Co.  and  was 
fitted  with  a  diaphragm  spring.  It  was  carefully  test- 
ed and  the  dial  calibrated  before  being  put  in  service. 

The  recording  pressure  gauge  was  a  modification 
of  the  Metropolitan  recording  gauge  made  by 
Schaeffer  &  Budenberg.  The  clockwork  in  it  was 
removed  and  the  paper  drum  driven  by  hand,  so 
that  a  record  of  indefinite  length  could  be  obtained. 
The  fact  that  this  paper  was  driven  by  hand  ex- 
plains the  irregularity  of  the  intervals  elapsing  be- 
tween the  passage  of  the  several  wheels  of  the  cars. 
This  gauge  also  had  a  maximum  registration  of  200 
Ibs.  per  sq.  in.  with  a  pen  travel  of  4  ins.,  the  width 
of  the  paper.  A  Bourdon  tube  was  used  as  the 
spring  for  this  gauge.  It  was  calibrated  for  each 
set  of  tests  by  the  Utka  gauge  and  its  indications 
marked  on  the  paper  on  which  the  record  was  taken. 

The  piping  and  all  spaces  filled  with  liquid  were 
so  arranged  that  air  pockets  were  entirely  eliminated 


and  before  work  was  commenced  it  was  definitely 
ascertained  that  the  whole  space  was  completely 
rilled  with  liquid  free  from  bubbles  of  air. 

The  speed  of  the  experimental  car  as  it  passed 
the  instrument  was  registered  by  means  of  two 
trips  placed  alongside  the  track  and  arranged  to  be 
struck  by  one  of  the  journal  boxes  of  the  car  as  it 
passed.  The  trips  closed  an  electric  circuit  passing 
through  one  of  the  coils  of  a  double  registering 
Morse  telegraph  instrument.  When  the  trip  was 
struck  by  the  journal  box,  the  circuit  was  tem- 
porarily broken  and  the  pen  lifted,  leaving  an  open- 
ing in  the  line  drawn  on  the  strip  of  paper  traveling 
through  the  instrument.  The  time  was  indicated 
by  a  clock  making  and  breaking  an  electric  circuit 
at  half-second  intervals.  This  circuit  passed  through 
the  other  coil  of  the  register.  The  two  records  were 
made  side  by  side  and  the  intervals  between  the 
breaks,  on  the  otherwise  continuous  line,  showed  the 
time  elapsing  between  the  striking  of  the  two  trips. 
These  trips  were  spaced  66  ft.  apart,  so  that  the  speed 
of  the  passing  car  could  be  readily  calculated.  Speci- 
mens of  these  records  are  shown  in  the  accompanying 
diagram  where  the  car  was  moving  at  9.14,  13.26, 
14.21,  2 1.8 1,  and  30.61  miles  per  hour,  respectively. 

Through  the  courtesy  of  the  Pittsburgh,  Cincin- 
nati, Chicago  &  St.  Louis  Ry.,  facilities  were  sup- 
plied for  making  this  investigation  of  wheel  stresses. 
The  instrument  was  placed  in  the  outer  rail  near  the 
end  of  a  curve  of  1,307  ft.  radius  or  about  4°  25'. 
The  elevation  of  the  outer  rail  was  3!  ins.,  which  is 
correct  for  a  speed  of  36.66  miles  per  hour.  At  the 
point  where  the  records  were  taken  the  car  was  well  in 


EXAMPLES  OP  LATERAL  THRCST 
TOTAL  WEIGHT, 


5107 

/730M1L£S  />£*  HOUR 

DIAGRAMS  OP   LOADED   COAL  CAR. 
OR  4°  «'   CURVE. 


OF  LATERAL  THRUST 
WITH  CARS  OF 


T10XS   OF   LOADED   COAL  TRAINS, 
LBS.   CAPACITT. 


on  the  curve,  with  the  trucks  set  in  die  normal  posi- 
tion, and  all  the  elements  of  entering  the  curve  were 
removed.  It  may  be  added  that  the  curve  was  a 
simple  one,  with  no  easement  at  either  end. 

On  the  approach  of  a  train,  or  the  experimental 
car,  an  initial  pressure  was  put  on  the  piping 
system,  in  order  that  the  movement  of  the  register- 
ing pen  might  be  reduced  to  a  minimum  and  with 
it  the  effect  of  the  inertia  of  the  parts.  This  initial 


it* 


pressure  was  varied  according  to  the  speed .  In  opera  - 
don  the  actual  movement  of  the  floating  rail  was 
imperceptible.  The  levers  divided  the  actual  move- 
ment by  five  at  the  diaphragm,  which  yielded  only 
enough  to  take  die  expansion  of  the  Bourdon  tube 
and  the  diaphragm  of  the  pressure  gauge,  when 
delivering  from  a  cylinder  6  in,  in  diameter. 

Records  were  taken  of  a  number  of  passing  trains, 
and  also  a  special  series  of  measurements  was  made 
with  a  loaded  coal  car  run  at  different  speeds  over 
the  apparatus.  Some  of  the  records  are  shown  in 
the  accompanying  diagrams, 

In  the  records  of  the  loaded  coal  trains,  taken  as 
they  pafffi,  no  memorandum  of  the  weights  of  the 
cars  was  obtained.  The  weights  were,  however, 
approximately  the  same,  and  yet  there  were  wide 
variations  in  the  lateral  thrusts  of  the  wheel  against 
the  rait  For  example:  In  the  train  moving  at 
9,35  miles  per  hour  these  thrusts  varied  from  2,260 
Ibs,  to  7,2 1 o  Jbs.,  with  an  average  of  4,835  Ibs.  On 
another  train,  moving  at  12x35  miles  per  hour,  the 
thrust  varied  from  7,070  Ibs.  to  10,605  Ibs.,  with  an 
average  of  8,205  Ibs.;  while  on  another,  moving  at 
4-04  miles  per  hour,  the  average  was  5,543  Ibs.,  with 
a  range  from  4450  to  6,635  ">*•  ^n  one  case  a  car  reg- 
istered a  thrust  of  16,175  Iks.  wnen  moving  at  14-35 
miles  per  hour.  This  wide  variation  in  the  lateral 
thrust  of  different  cars  in  the  same  train  at  the  instant 
of  passing  the  apparatus  was  still  more  strikingly 
shown  jn  the  senes  of  tesn  made  with  a  single  car. 

The  tests  with  a  single  car  consisted  of  33  runs  over 
the  apparatus,  at  speeds  varying  from  4.57  to  31-25 
miles  per  hour.  The  car  used  was  a  hopper-bottom 


coal  car  of  100,000  Ibs.  capacity  and  weighing, 
when  empty,  39,500  Ibs.  It  was  designated  as  of 
the  Gl  class  of  the  Pennsylvania  Lines  West.  The 
total  weight  of  the  loaded  car  was  142,300  Ibs. 

This  car,  after  being  started  some  distance  from 
the  apparatus,  was  cut  loose  from  the  engine  and 
allowed  to  drift  over  the  track  instrument. 

The  following  table  gives  the  records  that  were 
made: 


Test 
No. 

Speed. 
M.p.  H. 

Wheel 

No. 

Lateral  Thrust. 
Lbs. 

I 

4-57 

I 

2,470 

(4 

1C 

2 

1,415 

" 

" 

3 

1,695 

" 

" 

4 

1,415 

2 

7.63 

I 

1,695 

" 

" 

2 



" 

" 

3 

1,415 

" 

" 

4 



3 

10.43 

I 

»»S4S 

" 

" 

2 

1,770 

" 

u 

3 

1,695 

" 

ft 

4 

1,695 

4 

7.39 

i 

2,400 

" 

" 

2 

1,415 

u 

" 

3 

1,415 

" 

M 

4 

1,415 

5 

8.57 

i 

2,120 

(C 

2 

1,270 

H 

" 

3 

1,415 

" 

II 

4 

1,415 

6 

8.20 

i 

1,840 

" 

" 

2 

1,415 

" 

" 

3 

1,415 

4 

1,415 

118 


Test 

No. 

Speed. 
M.  p.  H. 

Wheel 
No. 

Lateral  Thrust. 
Lbs. 

7 

9.60 

I 

1,695 

" 

M 

2 

1,415 

<i 

H 

3 

1,270 

« 

«« 

4 



8 

IO.2I 

i 

3,250 

« 

M 

2 

3,"o 

u 

« 

3 

4,240 

« 

M 

4 

3,250 

9 

9.60 

i 

3.535 

« 

« 

2 

3,535 

«« 

<« 

3 

4,240 

{< 

(« 

4 

3»i95 

10 

9.60 

i 

3.535 

« 

(« 

2 

3,250 

« 

M 

3 

4,380 

<« 

M 

4 

3,250 

ii 

15.62 

i 

3,"o 

«« 

« 

2 

2,970 

« 

11 

3 

2,970 

« 

M 

4 

2,400 

12 

11.00 

I 

4,950 

" 

M 

2 

4,240 

ti 

It 

3 

3,96o 

«< 

(« 

4 

3,8i5 

I3 

I6.SS 

i 

4,525 

« 

« 

2 

3»535 

« 

M 

3 

4,525 

<i 

«« 

4 

3,395 

H 

I4.I8 

i 

3,8i5 

« 

« 

2 

3,535 

«< 

M 

«« 

3 

4 

5,935 
4,665 

IS 

12.63 

i 

3,393 

«< 

« 

2 

3,25o 

N 

« 

3 

4,857 

<« 

M 

4 

3,25° 

119 


Test 
No. 

Speed. 
M.  p.  H. 

Wheel 
No. 

Lateral  Thrust. 
Lbs. 

16 

13-33 

M 

I 
2 

4,810 
4,8  10 

« 

« 

«< 

3 

4 

7,350 
5,800 

TEST  OF   AUGUST   6TH,  1907. 

17 
«( 

9.14 
« 

2 

6,645 
5,655 

« 

«( 

3 

4,95° 

« 

« 

4 

4,240 

18 

13.26 

i 

8,055 

<( 

« 

2 

7,775 

N 

« 

3 

7,635 

« 

« 

4 

6,645 

19 

13.66 

i 

10,460 

«< 

« 

2 

7,490 

(« 

« 

3 



" 

« 

4 



2O 
«< 

13.27 
u 

i 

2 

7,210 

6,645 

M 

« 

3 

6,500 

« 

<« 

4 



21 

1  6.2  1 

i 

4,665 

«< 

(« 

2 



« 

«( 

3 

6,220 

«« 

H 

4 



22 

18.00 

i 

7,210 

« 

M 

2 

6,645 

« 

«i 

3 



« 

M 

4 



23 

(4 

17.58 
« 

i 

2 

6,785 
6,360 

(' 

II 

3 

7,775 

« 

(« 

4 

6,645 

24 

14.21 

i 

9,895 

(( 

«< 

2 

9,470 

« 

« 

3 

10,320 

« 

«« 

4 

8,480 

Test 
No. 

Speed. 
M.p.  H. 

Wheel 
No. 

Lateral  Thrust. 
Lbs. 

25 

10.91 

I 

2,825 

ii 

" 

2 



" 

" 

3 

3,110 

" 

" 

4 



26 

18.46 

i 

10,320 

" 

" 

2 

9,100 

M 

" 

3 

10,605 

M 

" 

4 

10,320 

27 

21.81 

i 

4,950 

" 

« 

2 



" 

" 

3 

7,490 

" 

" 

4 

5,230 

28 

19.03 

i 

16,785 

" 

" 

2 



M 

" 

3 

7,350 

" 

* 

4 

5,090 

29 

25.10 

i 

5.655 

" 

" 

2 

5'655 

" 

" 

3 

5.655 

II 

" 

4 

3.675 

30 

25.10 

i 

io,745 

II 

2 

9.330 

M 

" 

3 

10,180 

M 

" 

4 

9,615 

3J 

27.91 

i 

10,605 

" 

2 

9,895 

M 

II 

3 

9,615 

II 

" 

4 



32 

3i;25 

i 

10,035 

M 

2 

8,200 

" 

" 

3 

11,025 

" 

" 

4 

7,775 

33 

30.61 

i 

12,445 

M 

" 

2 

3 

11,310 
12,865 

4 

9,190 

I II 


/QOOO 


^6,000 


/O 


/S 


2O 


SO 


3S 


DIAGRAM    OF    LATERAL  THRUST    OF    LEADING   WHEEL    OF   FORWARD    TRUCK 
OF    LOADED    COAL    CAR.     TOTAL  WEIGHT,  142,300   LBS.,    ON   4°   25'    CURVE. 

The  column  headed  "Wheel  No."  indicates  the 
order  in  which  the  wheels  passed  over  the  apparatus. 
Thus:  I  indicates  the  front  wheel  of  the  forward 
truck;  2,  the  second  wheel;  3,  the  front  wheel  of  the 
rear  truck,  and  4  the  rear  wheel.  The  blank  spaces 
in  the  column  of  lateral  thrust  indicate  no  record 
obtained,  because  of  the  fact  that  the  initial  pressure 
put  on  the  apparatus  was  greater  than  the  wheel 


122 


thrust,  so  that  the  thrust  produced  no  movement  of 
the  pen.  Throughout  the  whole  series  of  tests  the 
weather  was  fine  and  the  rail  dry. 

For  convenience  of  reference  and  comparison  the 
lateral  thrusts  of  the  front  wheel  of  the  forward 
truck  have  been  plotted  on  the  accompanying  dia- 
gram. This  diagram  shows  graphically  the  wide 
variations  in  the  lateral  thrust  of  the  wheel.  From 
it  it  is  impossible  to  deduce  any  positive  ratio  be- 
tween the  speed  and  the  thrust,  but  it  shows  that 
there  is  a  relationship  and  that  the  higher  the  speed 
the  greater  the  thrust.  There  are  a  number  of 
records  for  the  first  wheel,  extending  from  about 
7.63  miles  an  hour  to  16.55  miles  an  hour  that  lie  in 
a  straight  line  drawn  from  just  below  the  record  of 
31.25  miles  an  hour  of  10,035  Ibs.  The  line  drawn 
through  these  points  is  represented  by  the  equation: 

T  =  333V-  800 

in  which 

V  =  Lateral  thrust  of  wheel  in  Ibs. 
T  =  Speed  in  miles  per  hour. 

This  must  be  regarded  as  a  tentative  formula  only 
and  one  which  evidently  will  not  hold  for  very  low 
speed.  But  from  the  records  that  have  been  obtained 
it  gives  the  lowest  values  and  therefore  it  cannot  be 
criticized  as  being  too  high. 

Attention  is  also  called  to  the  fact  that  the  pres- 
sure seems  to  increase  directly  as  the  speed  and  not 
as  the  square  of  the  speed  which  is  the  rate  of  in- 
crease of  the  centrifugal  force.  The  probable  rea- 
son for  this  is  that  none  of  the  speeds  recorded  were 
equal  to  or  exceeded  the  speed  corresponding  to 
the  superelevation  of  the  outside  rail.  Therefore, 


centrifugal  action  has  no  effect.  In  running  around 
a  curve  the  car  must  be  deflected  from  the  tangent 
at  a  certain  rate,  and  this  requires  a  certain  definite 
amount  of  power.  If,  then,  this  power  is  exerted  in 
a  short  period  of  time,  a  higher  pressure  will  be  put 
against  the  rail  than  if  the  time  was  longer,  and, 
therefore,  the  pressure  will  vary  inversely  as  the 
time.  So  that  if  the  car  passes  around  the  curve  in 
half  a  minute  the  pressure  will  be  twice  what  it 
would  be  if  a  minute  was  required.  Hence  the 
pressure  at  thirty  miles  an  hour  would  be  twice 
that  at  fifteen  miles  an  hour. 

When  the  speed  exceeds  that  for  which  the  super- 
elevation is  calculated  centrifugal  action  will  then 
begin  to  manifest  itself,  and  there  will  then  be  a 
more  rapid  rise  of  pressure  than  would  be  found 
from  the  equation  given  on  page  123.  This  additional 
increase  would  be  in  the  ratio  of  the  square  of  the 
speed.  For  example:  At  a  speed  of  36.66  miles 
per  hour  the  centrifugal  effect  is  balanced  by  the 
superelevation  of  the  outer  rail  on  the  curve  on 
which  these  investigations  were  made.  At  40  miles 
per  hour  the  centrifugal  force  is  1.19  times  as  great, 
and  this  19  per  cent,  additional  manifests  itself  as 
additional  lateral  thrust  above  that  called  for  by  the 
formula. 

Taking  the  car  under  consideration,  weighing 
142,300  Ibs.,  the  centrifugal  action  would  be  9,648 
Ibs.  at  36.66  miles  per  hour,  11,481  Ibs.  at  40 
miles  per  hour,  and  14,568  Ibs.  at  45  miles  per 
hour.  The  excess  centrifugal  force  to  be  dis- 
tributed among  the  four  wheels  of  the  car  at 
40  and  45  miles  an  hour  would  be,  therefore, 


124 


1,833  Ibs.  and  4,920  Ibs.  respectively.  If  25  per 
cent,  of  this  is  taken  by  the  front  wheel,  which 
is  a  low  estimate  of  what  would  actually  be  im- 
posed, there  would  be  an  extra  load  of  458  Ibs.  and 
1,230  Ibs.  added  to  the  stress  given  by  the  formula 
for  that  imposed  on  the  front  wheel.  This  then 
becomes 

11,408  Ibs.  at  36.66  miles  per  hour 
12,978  Ibs.  at  40  miles  per  hour 
15,415  Ibs.  at  45  miles  per  hour 

It  must  be  remembered  that  these  are  minimum 
values,  and  that  blows  due  to  soft  spots  in  the  track, 
kinks  in  the  curve,  bent  rails,  low  joints  and  cramped 
side  bearings  will  greatly  increase  this  thrust.  Suffi- 
cient data,  however,  has  not  yet  been  obtained  to 
warrant  any  estimate  of  how  much  this  increase 
would  be.  The  diagram  shows  that  stresses  far 
above  those  found  from  this  tentative  formula  are 
imposed  on  the  wheels. 

The  extreme  case  occurred  in  test  No.  19,  where 
the  thrust  was  6,711  Ibs.  in  excess  of  that  found 
from  the  formula.  If  the  blow  or  cramping  which 
caused  this  excessive  thrust  at  13.66  miles  per  hour 
was  to  occur  at  a  speed  of  45  miles  per  hour,  the 
thrust  that  might  be  expected  would  be  22,126  Ibs., 
and  if  it  were  to  be  increased  in  proportion  to  the 
speed  it  would  become  more  than  36,000  Ibs.  This 
may  be  an  extreme  and  exceptional  case,  but  the 
results  obtained  seem  to  indicate  that  at  least  as 
great  a  stress  as  this  should  be  provided  for. 

Referring  again  to  the  tests  of  flange  strength  made 
in  1905  by  Professor  Goss,  in  the  23  tests  that  were 


made,  the  pressures  required  to  break  the  flange 
ranged  from  47,750  Ibs.  to  109,900  Ibs.,  with  an 
average  of  75,874  Ibs.  This  gives  a  possible  factor 
of  safety  of  a  little  more  than  2.5  when  the  maximum 
stress  is  taken  at  30,000  Ibs.,  but  it  drops  to  a  little 
more  than  1.5  when  the  strength  of  the  weakest 
wheel  is  taken  as  the  basis  of  comparison.  This  is 
for  new  wheels.  When  they  have  become  somewhat 
worn  the  strength  of  the  flange  is  less  and  the  factor 
of  safety  is  decreased  still  more.  If  this  loss  of 
strength  in  the  old  wheel  is  taken  at  10  per  cent., 
because  of  metal  worn  away,  the  strength  of  the 
weakest  wheel  used  in  the  tests  referred  to  would  be 
42,975  Ibs.,  and  this  would  allow  a  factor  of  safety 
above  a  maximum  load  of  30,000  Ibs.  of  about  1.4. 

In  this  comparison  it  has  been  assumed  that  a  car 
of  100,000  Ibs.  capacity  will  deliver  the  maximum 
thrust  to  the  wheel  on  a  4^  degree  curve  at  45  miles 
per  hour.  This  assumption  was  made  because  the 
data  was  obtained  from  such  a  curve.  It  is  evident 
that  greater  stresses  would  be  imposed  on  curves  of 
sharper  radius.  The  outer  thrust,  where  centrifugal 
action  is  eliminated,  would  probably  vary  inversely 
as  the  radius  of  curvature.  There  is  no  data,  as  yet, 
to  support  this  position,  but  it  appears  probable. 
If  on  further  investigation  this  relation  is  found  to 
hold,  then,  instead  of  a  thrust  of  12,520  Ibs.  being 
put  on  the  wheel,  as  in  the  case  of  a  car  moving  over 
the  4°  25'  curve  at  40  miles  an  hour,  there  will  be  a 
thrust  of  nearly  22,800  Ibs.  when  the  same  speed  is 
maintained  over  a  curve  of  8°.  To  this  must  be 
added  the  extra  stresses  that  may  be  set  up  by  blows, 
cramping  of  the  wheels  between  the  rails,  the  binding 


126 


of  side  bearings  and  other  causes  which  may  result 
in  an  increase  of  the  normal  stress. 

But  one  weight  of  car  and  one  arrangement  of 
wheel  base  has  been  here  considered.  There  is,  as 
yet,  no  data  to  give  any  idea  as  to  the  effect  of  weight, 
its  distribution  on  the  wheels  or  the  height  of  the 
center  of  gravity,  all  of  which  are  undoubtedly 
important. 

On  the  other  hand,  in  this  discussion,  the  whole 
lateral  thrust  is  considered  as  resisted  by  the  flange. 
Under  ordinary  running  conditions  this  is  not  the 
case,  for  the  frictional  resistance  of  the  tread  of  the 
wheel  on  the  rail  must  be  subtracted  from  the  total 
thrust.  In  the  car  under  consideration  the  weight 
on  the  front  wheel  was  17,900  Ibs.  If  the  coefficient 
of  friction  is  taken  at  0.25  then  4,475  Ibs.  should  be 
subtracted  from  the  pressure  given.  This  would 
reduce  the  maximum  pressure,  as  it  has  been  cal- 
culated for  a  speed  of  45  miles  per  hour,  to  31,525 
Ibs.  and  the  probable  minimum  to  10,930  Ibs.  It 
must  be  remembered,  however,  that  the  frictional 
resistance  is  apt  to  fail  suddenly  and  that  at  all  speeds, 
even  where  the  frictional  resistance  of  the  tread  on 
the  rail  is  greater  than  the  lateral  thrust,  there  must 
be  a  pressure  on  the  flange  in  order  to  effect  the 
deflection  of  the  car  on  the  curve. 

In  this  comparison  the  front  wheel  of  the  leading 
truck  only  has  been  considered,  because  it  is  on  this 
wheel  that  the  heaviest  lateral  thrust  is  imposed. 
The  table  shows  that,  in  general,  the  maximum 
lateral  thrust  is  on  the  first  wheel;  the  thrust  on  the 
second  is  less;  on  the  third  it  falls  between  the  first 
and  the  second,  and  on  the  fourth  it  is  the  lowest. 


In  considering  the  advisability  of  using  cast  iron 
wheels  under  high  capacity  cars,  it  should  be  borne 
in  mind  that  the  cast  iron  wheel  averages  approxi- 
mately one-half  the  life  under  the  cars  of  IOO,OQO 
Ibs.  capacity  that  it  does  under  cars  of  60,000  Ibs. 
capacity.  The  use  of  the  heavy  braking  pressure  on 
long  grades  has  been  the  cause  of  many  failures, 
because  of  the  additional  strains  set  up  due  to  the 
heating  by  the  brake  shoe.  There  is  a  consequent 
expansion  of  the  rim,  and  the  actual  resisting 
strength  of  the  flange  is  lowered  below  that  shown 
in  the  laboratory  tests,  which  were  made  with  the 
wheel  cold  and  the  metal  at  its  maximum  strength. 
Roads  having  long,  steep  grades  usually  have 
numerous  sharp  curves  also,  and  the  wheels  are 
likely  to  be  subjected  to  the  most  severe  stresses 
when  they  are  least  able  to  resist  them.  If  the  lateral 
thrust  on  the  flanges  of  wheels,  under  a  loaded  car  of 
100,000  Ibs.  capacity,  runs  up  as  high  as  30,000  Ibs., 
and  the  actual  breaking  strength  of  the  flanges  of 
cast  iron  wheels  varies  from  45,000  Ibs.  to  105,000 
Ibs.  under  the  most  favorable  conditions,  the 
question  seems  pertinent,  is  it  safe  to  use  such 
wheels  under  high  capacity  cars,  in  view  of  the  fact 
that  cast  iron  wheels  deteriorate  rapidly  with  wear 
and  successive  brake-shoe  heating? 

The  answer  depends  upon  what  the  user  deems  a 
proper  factor  of  safety  for  such  service  or  the 
risks  he  can  afford  to  run. 


128 


PRESENTATION   OF   THE  ADVAN- 
TAGES    CLAIMED     FOR    THE 
SCHOEN    SOLID     FORGED    AND 
ROLLED    STEEL   WHEEL   AS 
BASED    UPON    THE    RESULT    OF   THE 
INVESTIGATIONS  SET  FORTH    IN  THE 
FOREGOING     CHAPTERS,     TOGETHER 
WITH    THE    DEMONSTRATION    OF 
SERVICE    TESTS. 

BY  THE  SCHOEN  STEEL  WHEEL  CO. 

THE  investigations  of  the  physical  and  chemical 
properties  of  car  wheels  outlined  in  the  preceding 
chapters  show  what  is  being  done  in  the  manufac- 
ture of  car  wheels  and  steel  tires  and  the  require- 
ments which  must  be  met  in  service.  Acting 
upon  the  accepted  theory  that  steel  must  have  a 
maximum  amount  of  work  put  upon  it  to  insure  its 
integrity  and  efficiency,  consideration  of  cast  steel 
wheels  has  been  ignored.  It  has  been  shown  that 
the  metal  in  the  Schoen  solid  forged  and  rolled 
steel  wheel  is  in  all  respects  equal  to  if  not  better 
than  the  metal  in  standard  brands  of  steel  tires  and 
wheels  as  regards  physical  properties.  It  would 
naturally  be  expected  then  that  these  wheels  should 
compare  favorably  in  wearing  qualities  and  strength 
in  actual  service.  This  expectation  has  been  com- 
pletely fulfilled  by  the  wheels  which  have  been  running 
under  tenders,  freight  and  passenger  cars,  and  street 
and  interurban  electric  cars.  The  Schoen  solid  forged 
and  rolled  steel  wheel  has  been  found  to  give  mater- 
ially greater  mileage  for  the  same  limit  of  wear  than 
steel-tired  wheels  under  exactly  the  same  conditions. 


1*9 


TOTAL 


N9503 
M/LEXQE  P£ft  fc 


-  322/7 


N2522 

TOTAL  WEAR  .346  M/LEAGE  PEfi^' WEAfi- 33/43 
WEAR   OF    SCHOEN   STEEL    WHEELS   UNDER    POSTAL   CARS. 

MITFAPF   OF/513   AN°   ^=154,732. 
MILEAGE   OF  j  ^   ANJ)   522  =  184i539. 


130 


As  a  fair  example  of  what  has  been  done  with 
these  wheels  in  heavy  passenger  car  service  the  fol- 
lowing record  is  given  of  a  test  made  on  wheels 
placed  under  postal  car  No.  6545,  running  on  the 
Pennsylvania  Railroad  between  New  York  and  St. 
Louis:  The  car  weighed  154,000  Ibs.,  carried  on 
two  six-wheel  trucks,  giving  a  weight  per  wheel  of 
12,833  Ibs.  The  wheels  under  this  car  ran  184,539 
miles  with  a  wear  ranging  from  .348  in.  to  .378 
in.,  or  an  average  of  .365  in.  The  mileage  per 
iV  in.  of  wear  was  25,618.  The  tread  was  main- 
tained at  all  times  in  smooth  condition  and  the 
wear  on  all  of  the  wheels  was  remarkably  uniform 
and  even. 

Twelve  pairs  of  wheels  from  the  same  lot  were 
placed  under  one  truck  each  of  four  postal  cars  on 
various  runs.  The  average  mileage  of  these  wheels 
up  to  the  time  of  first  turning  was  109,018,  with  a 
minimum  of  87,375  mn<es  and  a  maximum  of  141,170 
miles.  The  pair  of  wheels  giving  this  maximum 
mileage  were  worn  .3185  in.  and  .2785  in.  respectively. 
An  average  wear  of  .2597  in.  in  109,018  miles  was 
obtained  from  all  12  pairs,  which  is  at  the  rate  of 
419,703  miles  per  inch  or  26,231  miles  per  -^  in. 
of  wear.  If  the  amount  of  metal  removed  by  turning 
is  added  to  the  actual  wear  these  figures  are  reduced 
to  234,202  miles  per  inch  and  14,638  miles  per  yg- 
in.  of  wear.  The  causes  of  removal  of  these  wheels 
were  3  pairs  for  worn  treads,  3  pairs  for  cut  journals, 
I  pair  for  a  loose  wheel,  I  pair  for  a  thin  flange  and 
3  pairs  for  hollow  and  built-out  flanges.  At  the 
time  this  record  was  taken  the  remaining  pair  of 
wheels  had  not  been  removed. 


In  electric  traction  work,  where  the  service  is 
much  more  severe  than  on  steam  roads,  be- 
cause of  the  greater  number  of  stops  and  the  bad 
condition  of  the  rails,  and  because  of  the  fact  that 
the  majority  of  the  wheels  are  motor  driven,  the 
mileage  is  less,  but  is  still  sufficiently  high  to  show  a 
decided  advantage  for  the  solid  forged  and  rolled 
steel  wheel  over  the  cast  iron  wheel.  The  records  of 
the  Brooklyn  Rapid  Transit  Co.  show  that  from 
these  wheels  there  was  obtained  a  mileage  per  TV  in. 
of  wear  of  6,500  miles  under  electric  freight  cars 
running  on  the  surface  lines,  and  from  8,520  miles  to 
9,750  miles  under  motor  passenger  cars.  This  is  at 
the  rate  of  about  .0961  in.  and  .0641  in.  respectively 
per  10,000  miles  run,  with  the  wheels  still  remaining 
in  such  good  condition  that  turning  was  unnecessary. 
Still  better  results  were  obtained  with  these  wheels 
under  elevated  motor  cars  of  the  same  company. 
The  records  show  wear  at  the  rate  of  TV  in.  per 
10,850  miles  run,  or  a  reduction  of  .0575  in.  per 
10,000  miles.  The  flange  and  tread  were  still  in 
good  condition  after  having  been  worn  down  f  in. 
and  more.  The  accompanying  tables  and  diagrams 
illustrate  in  a  striking  manner  the  remarkable  service 
obtained  by  these  wheels  on  this  road  and  substan- 
tiate all  of  the  claims  made  for  them  for  electric 
railway  work. 

From  the  data  here  presented  it  will  be  a  simple 
matter  to  compare  the  value  of  the  solid  forged  and 
rolled  steel  wheel  with  the  value  of  the  cast  iron 
wheel  in  similar  service.  Dividing  the  life  of  the 
steel  wheel  by  the  life  of  the  cast  iron  wheel  gives 
the  number  of  cast  iron  wheels  required  for  an 


134 


NS  21773 


WEAR  OF  SCHOEN  STEEL  WHEELS  ON  BROOKLYN  RAPID  TRANSIT  R.R. 


133 


N2  920+ 


WEAR  OF  SCHOEN  STEEL  WHEELS  ON  BROOKLYN  RAPID  TRANSIT  R.R. 


134 


WEAR  OF  TREAD  — SCHOEN  ROLLED  STEEL  WHEELS. 


1 

3 

13 

i 

1 
<u    • 

(3 

0 

t 

£ 

1 

| 

1 

SJ 

g 

1 

fc 

£ 

in 

•g 

(3 

8 

& 

I 

S  s 

'5  «j 

S   . 

S   tt 

Type  of  Truck. 

13 

0 

S 

S3 

c 

^ 

0 

•2§ 

"2  E 

> 

3 

§ 

1 

1 

i 

Jo' 

S 

1 

^ 

M 

•§, 

S 

£ 

1 

1  s 

.1 

1 

S 

5 

8 

& 

1 

0 

H 

Lbs. 

In. 

In. 

In. 

In. 

Freight  Truck     . 
Motor  Truck  .     . 

9358 
9359 
9199 

Flanged 

4,394 
4,394 
10,825 

33 

30^8 
30^8 

19,500 

19,500 

58,500 

None 

.1923 
.1923 
.1282 

58,500 
58,500 
204,100 

"          "     .     . 

9204 

1 

10,825 

33 

32}^ 

58,500 

.1282 

% 

204,100 

"          " 

9188 

' 

7,482 

33 

32% 

42,600 

.1466 

y% 

85,400 

ElevatedRailway 

9190 

7,482 

33 

32% 

42,600 

.1466 

y* 

85,400 

Coach     .     .    . 
ElevatedRailway 

"773 

Flangeless 

4,262 

30 

29%6 

70,650 

.115 

18Ae 

10,8  1  1 

Coach     .     .     . 

21774 

4,262 

30 

*9^ 

70,650 

.1061 

« 

10,811 

equivalent  mileage.  The  cost  of  renewals  of  the 
cast  iron  wheels  must  be  added  to  the  first  cost 
and  credit  allowed  for  the  scrap  value  of  the  old 
wheels  removed. 

There  are  other  items  of  cost,  however,  which, 
although  difficult  to  accurately  estimate  are,  never- 
theless, important.  It  must  be  remembered  that 
each  car  has  an  earning  capacity  which  is  lost  when- 
ever the  car  is  in  the  shop  for  renewals  or  repairs, 
and  this  should  be  credited  to  the  steel  wheel  which 
involves  no  such  loss.  Again,  if  the  number  of  shop- 
pings for  wheel  defects  can  be  materially  reduced 
the  same  volume  of  traffic  can  be  handled  with  fewer 
cars,  thus  saving  investment  in  rolling  stock  and, 
what  is  almost  as  important  in  large  cities,  saving  in 
expensive  storage  space.  These  advantages,  tangible 
and  intangible,  have  been  so  thoroughly  demonstrated 
to  street  railway  officers  by  the  experience  of  a  few 


'35 


33-IN.    STREET-CAR    WHEEL. 


34-IN.    STREET-CAR    WHEEL. 

roads  which  early  began  to  use  solid  steel  wheels, 
that  there  is  a  large  and  growing  demand  for 
them  in  every  class  of  electric  service.  For  inter- 
urban  roads  especially,  where  the  speeds  are 
frequently  as  high  as  those  obtained  on  steam 
railroads,  solid  steel  wheels  have  been  generally 
adopted  for  reasons  of  safety.  The  solid  steel 


136 


33-IN.  WHEEL    FOR    THE    UNITED    ELECTRIC    RAILWAYS    AND    ELECTRIC 
CO.  OF    BALTIMORE,  MD. 


34-IN.  WHEEL  FOR  CITY  AND  INTERURBAN  SERVICE,  DESIGNED  FOR  SANDERSON 
PORTER,  CONTRACTORS  AND  ENGINEERS. 

wheel  offers  all  of  the  advantages  of  wear  claimed 
for  the  steel-tired  wheel  at  a  much  smaller  cost, 
and  in  addition  greater  safety,  because  of  the  im- 
possibility of  parts  coming  loose.  When  compared 
with  steel-tired  or  built-up  wheels,  in  which  the 
parts  are  shrunken  on  or  bolted  in  place,  and 
therefore  liable  to  become  slipped  under  the  com- 
bined effect  of  expansion  due  to  brake-shoe  heat- 
ing and  the  torque  of  the  motor,  the  advantages 
of  a  solid  steel  wheel  for  traction  purposes  become 
immediately  apparent. 


i37 


a3-IN.    STREET-CAR    WHEEL    FOR     NEW    YORK    CITY    RAILWAY    CO. 

-ai\- 


34-IN.   STREET-CAR    WHEEL    FOR    PENNSYLVANIA    AND    MAHONING    VALLEY 
TRACTION    CO. 

The  solid  forged  and  rolled  steel  wheel  was  origi- 
nally developed  to  meet  the  severe  requirements  of 
service  under  high  capacity  freight  cars  and  it  is  in 
this  field  that  it  has  the  widest  possibilities  of  appli- 
cation. That  there  is  a  demand  for  these  wheels  is 
shown  by  the  fact  that  more  than  150,000  are  now 
in  use,  55,000  of  them  in  service  under  100,000  Ibs. 
capacity  cars,  and  the  number  is  steadily  increasing. 

It  is  difficult  to  make  an  estimate  of  the  mileage 
cost  of  freight  car  wheels  because  of  the  incomplete 
records  usually  kept.  From  the  best  statistics  avail- 
able, however,  it  appears  that  the  mileage  obtained 
from  cast  iron  wheels  under  100,000  Ibs.  capacity 
cars  is  between  25,000  miles  and  30,000  miles. 


138 


33-IN.   STEEL  WHEEL. 


r 


34-IN.    SUBWAY    MOTOR-TRUCK    WHEEL   FOR    THE    INTERBOROUGH    RAPID 
TRANSIT    CO.,   NEW  YORK. 

From  the  tests  made  of  Schoen  solid  forged  and  rolled 
steel  wheels  under  postal  cars  on  the  Pennsylvania 
Railroad  it  was  found  that  there  was  obtained  an 
average  mileage  of  14,638  per  TV  in.,  including  wear 
and  turning.  Under  heavy  tenders,  the  mileage 
averaged  7,000  per  ^  in.  of  wear  and  turning.  The 
average  of  these  two  figures,  10,800  miles  per  -&  in. 
of  wear  and  turning,  may  be  taken  as  the  probable 
average  service  which  can  be  obtained  from  these 
wheels  under  high  capacity  freight  cars.  The 
wheels  furnished  to  the  Pennsylvania  Railroad  for 
freight  cars  have  a  rim  2  in.  thick  with  limit  groove 
for  wear  cut  f  in.  in  from  the  inner  edge.  This  gives 


139 


U 34' Dl 

_|_ , 


34-IN.   STREET-CAR    WHEEL   FOR    CHICAGO    CITY    RAILWAY   CO. 


r 


34-IN.   STREET-CAR    WHEEL    FOR    CONSOLIDATED    RAILWAY    CO., 
NEW    HAVEN,    CONN. 

a  wearing  thickness  of  ij  ins.  available  for  service. 

At  10,800  miles  per  ^  in.  of  wear,  the  total  mileage 

which  can  be  obtained  from  these  wheels  is  20  x 

10,800=216,000  miles  as  against  30,000  miles  for  cast 

iron  wheels,  or  a  little  more  than  seven  times  the  life. 

If  the  first  cost  of  a  cast  iron  wheel  is  taken  at  $10 

and  its  scrap  value  at  $5,  then  the  cost  of  cast  iron 

wheels  to  give  a  life  equivalent  to  the  life  of  one 

Schoen  solid  forged  and  rolled  steel  wheel  would  be: 

7  cast  iron  wheels  at  $10  each  $70 

7  scrap  wheels  (credit)  at  $5  each  $35 


Actual  cost  of  cast  iron  wheels 


140 


AXLE    AND    WHEEL    DESIGN    SUBMITTED   BY    THE    SCHOEN    STEEL   WHEEL   CO. 

AS    REQUESTED    BY    THE    CENTRAL    ELECTRIC    RAILWAY    COMMITTEE    ON 

STANDARDIZATION    FROM    THEIR    REPORT    DATED    MAY   23,   1907. 


L 


AXLE    AND  WHEEL    DESIGN    SUBMITTED    BY    THE    SCHOEN    STEEL  WHEEL   CO., 

AS    REQUESTED    BY    THE    CENTRAL    ELECTRIC    RAILWAY    COMMITTEE    ON 

STANDARDIZATION    FROM  THEIR    REPORT   DATED    MAY  23,  1907. 


|4-«A— idSB*F— 63' W£ 

I JL _  77' -jj— H 


K 
P 

-f 


AXLE    AND    WHEEL   DESIGN   SUBMITTED    BY    THE   SCHOEN   STEEL   WHEEL   CO. 

AS    REQUESTED   BY    THE   CENTRAL   ELECTRIC    RAILWAY    COMMITTEE    ON 

STANDARDIZATION    FROM   THEIR    REPORT    DATED    MAY   23,  1807. 


r 


AXLE    AND    WHEEL    DESIGN   SUBMITTED    BY    THE   SCHOEN   STEEL   WHEEL  CO. 

AS    REQUESTED   BY    THE    CENTRAL   ELECTRIC    RAILWAY    COMMITTEE    ON 

STANDARDIZATION,   FROM    THEIR    REPORT    DATED    MAY   23,   1907. 


142 


The  original  cost  of  the  solid  forged  and  rolled 
steel  wheel  may  be  taken  at  $20  and  its  scrap  value 
at  the  end  of  its  life  at  $5.  Its  total  cost,  therefore, 
would  be  $15  as  against  $35  for  the  equivalent  num- 
ber of  cast  iron  wheels  required  to  give  the  same 
mileage.  It  is  assumed  that  the  cost  of  turning  the 
solid  steel  wheel  the  required  number  of  times  during 
its  life  would  equal  the  cost  of  removing  and  re- 
placing the  cast  iron  wheels  on  the  axle. 

The  accompanying  diagram  shows  graphically 
the  comparative  mileage,  cost  and  strength  of 
the  ordinary  cast  iron  wheel  and  the  Schoen 

MILEAGE    Of   CAST   IRON    WHCCL 
MlieAG^OFSCHOENFORGE^ANDROLLEDSTEEL    WMEEl 

COST   PER   1000    MttES   OF   CAST   IRON    WHEELS    DURING    LIFE    OF   ONE    SCHOEN    STEEL   WHEEL 
COST    PER    '000    MILES  OF   ONE   SCHOEN    STEEL   WHEEL 

CAST    IRON    WHEEL   BASED    UPON    ITS    ELASTIC    LIMIT 


CHART    OF    COMPARATIVE    VALUES    OF    THE    SCHOEN    FORGED    AND    ROLLED 

STEEL  WHEEL,   AND    THE    CAST    IRON    WHEEL    FOR    LARGE    CAPACITY 

FREIGHT    CARS    AND    COACHES. 

solid  forged  and  rolled  steel  wheel.  The  first 
two  lines  show  the  comparative  mileage,  the  next 
two  show  the  comparative  cost  per  1,000  miles 
run,  and  the  last  two  lines  show  the  comparative 
safety  of  the  two  wheels  based  on  the  elastic 
limits  of  the  metal  of  which  they  are  made.  The 
mileage  is  as  7  to  I  in  favor  of  the  steel  wheel  and  the 
cost  per  1,000  miles  is  as  2  to  i  in  its  favor.  The 
elastic  limit  of  cast  iron  as  shown  on  the  chart  is 


143 


that  given  by  Unwin:  10,500  Ibs.  in  tension  and 
21,500  Ibs.  in  compression  with  a  mean  of  16,000  Ibs. 
The  elastic  limit  of  the  steel  wheel  is  taken  at  107,457 
Ibs.,  a  ratio  of  6.7  to  i  in  favor  of  the  steel  wheel. 
If  the  actual  breaking  strength  of  the  flanges  had  been 
used  in  proportioning  the  relative  lengths  of  these 
lines  their  ratio  would  have  been  as  8.6  to  i  in  favor 
of  the  steel  wheel  as  against  the  old  M.  C.  B.  stand- 
ard cast  iron  wheel  and  5.3  to  I  in  favor  of  the  steel 
wheel  as  against  the  new  reinforced  flange  cast  iron 
wheel.  It  is  evident,  therefore,  that  the  ratio  of  6.7 
to  i,  as  given  on  the  chart,  is  conservative. 

Cast  iron  wheels  under  high  capacity  cars  are  a 
known  source  of  danger,  and  on  most  mountain  roads 
a  careful  inspection  of  every  wheel  is  made  when  a 
freight  train  stops  at  the  foot  of  a  long  grade.  This 
costs  time  and  money,  and  even  then  the  inspec- 
tion is  not  always  successful  in  detecting  incipient 
failures  which  develop  later  with  disastrous  results. 
The  loss  of  earning  capacity  of  cars  standing  idle 
awaiting  shopping  for  wheel  defects  is  important 
in  times  of  congestion  of  traffic.  It  is  a  fact  that 
many  roads  are  prevented  from  realizing  the  full 
benefit  of  large  overload  carrying  capacity  simply  be- 
cause the  cast  iron  wheels  are  not  considered  safe 
to  carry  such  loads. 

In  the  foregoing  pages  many  and  important  ad- 
vantages of  the  Schoen  solid  forged  and  rolled  steel 
wheel  have  been  demonstrated.  Careful  examina- 
tions of  the  metal  of  which  the  wheel  is  made  have 
shown  it  to  possess  better  physical  properties  than 
the  best  steel  tires  and  wheels  on  the  market.  Ex- 
perience in  service,  with  wheels  under  freight  and 


144 


passenger  cars,  locomotive  tenders  and  electric 
cars,  proves  that  the  wearing  quality  is  superior 
to  the  best  of  its  competitors.  The  investigation 
of  the  lateral  thrust  of  the  wheel  against  the 
rail  gives  conclusive  evidence  that  the  cast  iron 
wheel,  even  when  made  of  the  best  material  and 
with  the  flange  reinforced  as  in  the  latest  designs,  is 
not  safe  under  high  capacity  cars  at  any  but  the 
lowest  speeds.  Finally,  it  has  been  shown  that  the 
solid  forged  and  rolled  steel  wheel  can  be  applied 
under  freight  cars  in  place  of  cast  iron  wheels  with 
an  actual  saving  of  $7  per  100,000  miles  run,  or  $56 
per  100,000  car  miles.  In  considering  the  question 
of  car  wheels  for  any  service,  therefore,  from  the 
standpoint  of  safety,  mileage  or  cost,  the  solid  forged 
and  rolled  steel  wheel  stands  in  front  of  all  others. 


The   Schoen   Steel  Wheel 
Company's  works  at 
McKees  Rocks,  Pa. 


149 


Hydraulic  presses,  each  with 
a  capacity  of  eighteen  million 
pounds,  are  used  to  forge 
the  Schoen  Solid  Steel 
Car  Wheel. 


The  most  ingenious 
mechanism  is  required  tc 
roll  and  finish  a  Schoen 
Solid  Steel  Car  Wheel. 


153 


One  of  the  electric 
manipulators  used  for 
handling  the  steel  blooms  i 
the  manufacture  of  Schoe 
Solid  Steel  Car  Wheels. 


Various  types  of  hydraulic 
presses  are  used  in  forging 
Schoen    Solid    Steel 
Car  Wheels. 


'55 


It   :  .       .,,'  .--..•  •  •        « 

.,     fj-        f    ?•'  *•   ».      * 


Twelve  hundred  horse- 
power engines  are  coupled 
each  rolling  mill  used  in  I 
manufacture    of  Schoen 
Solid  Steel  Car  Wheels. 


«57 


These  hydraulic  presses  wer< 
all  especially  designed  to 
forge  Schoen  Solid  Steel 
Car  Wheels. 


'59 


View  in  one  of  the  power 
houses  of  The  Schoen  Steel 
Wheel  Company's  plant 
at  McKees  Rocks,  Pa. 


161 


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